As they enter the final quarter of calendar year 2022, many investors are probably wondering when the sell-off will end. This year has tested the patience of even the most experienced investors as the tech-heavy Nasdaq Composite is down over 30% from its all-time high while the S&P 500 remains down over 20%. 

The silver lining of the market sell-off is that it gives investors the chance to form starting positions in companies at far lower valuations than in years past. Investors who like to dollar-cost average a portion of their income into their favorite stocks will be able to accumulate more shares without having to increase their savings rate -- which can be particularly beneficial for folks who are still early in their investment journeys. Down between 39% and 88% from their all-time highs, Roku (ROKU -1.34%), NovoCure (NVCR -0.65%), and Paycom Software (PAYC 0.08%) stand out as three growth stocks worth buying in October and holding for decades.

However, there are also plenty of attractive buys for risk-averse investors focused on capital preservation, supplementing income in retirement, or generating passive income. United Parcel Service (UPS -0.55%) and ExxonMobil (XOM -0.63%) have competitive advantages to support dividend raises over time. Here's what makes each of these top stocks a great buy now.

A child smiles while playing in the red, orange, and yellow autumn leaves.

Image source: Getty Images.

Roku looks like a bargain-bin value stock nowadays

Anders Bylund (Roku): I have been pounding the table about Roku for months, arguing that the stock is undervalued given the company's massive market opportunity. Of course, share prices have continued to slide due to inflation and anti-inflation efforts. High-octane growth stocks are just not an easy sell right now.

But that won't stop me from recommending Roku again, this time more than 80% below the stock's 52-week high. The trick is to ignore the short-term market swings and focus on Roku's enormous target market. Over time, old-school broadcasting technologies such as cable and satellite TV are destined to become relics, replaced by cheaper and better media-streaming services. And Roku happens to be the leading provider of streaming media platforms in Europe, North America, and Latin America.

It doesn't matter to Roku investors which streaming services end up with the largest market shares in the long run. All of them essentially have to support the Roku platform, since the company controls a large slice of the global streaming market. As long as the streaming industry as a whole continues to grow, Roku's business and stock should follow suit.

Furthermore, Roku has paid off all of its long-term debt and holds $2 billion of cash on its balance sheet. The company's financials are robust enough to handle years of soft TV sales and negative cash flows, if necessary. So you don't even have to assume Roku's market will pick up steam right away, because this juggernaut can handle a short-term challenge.

Meanwhile, the stock is trading at the lowest price-to-sales ratio in its history. Changing hands at just 2.6 times trailing sales, Roku's shares are found in the same ballpark as some well-regarded value stocks.

That's just ridiculous.

Beyond the economy-based market fears, Roku remains a powerful growth stock with decades of market-stomping returns ahead of it. Roku is a no-brainer buy in October.

Macroeconomic issues don't matter much to this stock

Keith Speights (NovoCure): The reasons behind the stock market decline are interconnected. Inflation is high, resulting in the Federal Reserve raising interest rates, which caused investors to worry more about a recession. But these macroeconomic issues simply don't matter much to NovoCure.

The biotech stock has taken shareholders on a roller-coaster ride this year, for sure. However, NovoCure is handily beating the S&P 500 and other major market indexes in 2022.

How is NovoCure defying the market downturn? Investors understand what does matter for the company -- its late-stage clinical studies evaluating Tumor Treating Fields (TTFields), a therapy that uses electrical fields to disrupt tumor division.

NovoCure has already won regulatory approvals for TTFields in treating glioblastoma (an aggressive type of brain cancer) and mesothelioma (cancer resulting from exposure to asbestos). It's hoping to expand those indications to include types of cancer that impact a much greater number of patients.

The company plans to announce results from its pivotal Lunar study of TTFields in treating non-small-cell lung cancer in early 2023. Data from late-stage studies targeting ovarian cancer and brain metastases should be on the way later next year. NovoCure also expects to report results from the late-stage study of TTFields in treating pancreatic cancer in 2024.

These four indications represent a market opportunity that's 14 times bigger than NovoCure's current market. If the company's late-stage studies are successful (and I think the chances appear to be pretty good), NovoCure could be about to deliver tremendous growth. Buying the stock in October before the Lunar data readout could pay off handsomely.

One of the most innovative companies in the world

Trevor Jennewine (Paycom Software): Paycom provides human capital management (HCM) software that helps businesses manage all aspects of the employee lifecycle, from recruitment through retirement. Its cloud platform addresses application tracking, scheduling, training, and payroll, among other back-end processes.

That broad utility gives Paycom an edge as most organizations currently stitch together multiple point solutions in an effort to create a comprehensive platform. But challenges with system integration often force organizations to manage employee data across multiple databases, creating an administrative nightmare. Paycom built its software on a single system of record, eliminating the cost and complexity created by a patchwork of disparate products.

Last year, the company further differentiated itself with the debut of Beti (Better Employee Transaction Interface), the first employee-driven payroll software in the HCM industry. Beti reduces administrative burden by asking employees to review and approve their paychecks prior to processing, which leads to fewer errors and greater operational efficiency. Thanks to Beti, Fast Company recognized Paycom as one of the world's most innovative companies in 2022.

Not surprisingly, Paycom continued to post strong financial results over the past year. Revenue climbed 30% to $1.2 billion and earnings rose 36% to $3.93 per diluted share. But management estimates Paycom has only captured "5% of a very large and growing" total addressable market, and the company is executing on a solid growth strategy to capitalize on that. For instance, Paycom is working to expand and densify its sales force. It opened five new sales offices in the last year, and CEO Chad Richison says those offices will contribute meaningfully to revenue by 2024.

More broadly, Paycom has demonstrated its capacity for innovation, and that quality should keep its business growing in the years ahead. While shares currently trade at a pricey 85.3 times earnings, that's a discount compared to its five-year average of 96.6, and its valuation could come down in a hurry if the company maintains its current growth trajectory. That's why this stock is a smart buy in October.

A market leader at a bargain bin price

Daniel Foelber (United Parcel Service): UPS stock is down in a good way. And what I mean by that is it's down for mostly macroeconomic reasons and a downturn in the business cycle, not because of any blunders by the company itself.

During a widespread market sell-off, stocks can fall for myriad reasons. Sometimes, a steep sell-off is warranted if a company is burning through cash and is reliant on debt or diluting its stock to get by. Or management overexpanded the business and weakened the balance sheet. Or the company is losing its competitive advantage and can't accurately chart a path toward long-term growth.

UPS falls into none of these categories. In fact, its execution gives investors every reason to scoop up shares on sale in October. UPS has posted impressive growth and record earnings, all the while keeping a lid on capital expenditures and more than doubling its dividend in seven years. The company's efficient use of capital is unparalleled in the package delivery industry.

On its fourth-quarter 2021 earnings call, UPS said it expected to achieve its 2023 goals (which were already ambitious) one year early. Those goals call for 2022 revenue of $102 billion (an all-time high), an operating margin of 13.7% ( which would be a 10-year high), and a return on invested capital above 30%. UPS is ahead of schedule as its trailing-12-month revenue is already above $100 billion and its operating margin is 13.6%.

UPS stock has fallen in recent weeks in response to fears of slowing package delivery volumes and a general slowdown in its business due to a recession. And while it's true the company's growth is already slowing compared to its torrid pace in 2021 and 2022, the fact the company is still likely to hit its 2023 goals early is impressive. With a price-to-earnings ratio of just 13.3 and a dividend yield of 3.7%, UPS is an established and well-rounded company with a high yield that investors can buy at an inexpensive valuation.

One earnings report to watch closely this month

Neha Chamaria (ExxonMobil): Crude oil prices are falling and so is ExxonMobil stock. This sell-off in Exxon shares over the past month, though, makes it a top-notch stock you'll want to pay close attention to in October. I'll give you three broad reasons why.

First, ExxonMobil's quarterly numbers are due for release later this month, and I expect solid year-over-year growth in its top and bottom lines. Second, Exxon also typically hikes its annual dividend around this time. Third and more importantly, ExxonMobil is now in a position to make money even at significantly lower Brent crude oil prices.

The thing is, the company is aggressively cutting costs to bring down its breakeven oil price, or the Brent crude price at which the company can generate enough cash flows to fund its planned capital expenditures and maintain its dividend payout. Having already slashed its breakeven oil price to $41 per barrel last year, Exxon is now targeting a level of only around $37 per barrel between 2022 and 2023, and just about $30 per barrel by 2030. For perspective, Brent crude is hovering around $87 per barrel as of this writing.

A lower breakeven makes Exxon's cash flows and dividends more resilient to the volatility in oil prices. For those in the know, ExxonMobil is a Dividend Aristocrat, and it'll likely announce its 40th consecutive annual dividend hike this month alongside its third-quarter numbers.

The third quarter should be another strong one for Exxon since oil prices were still much higher in recent months compared with last year. Its free cash flow (FCF), in fact, more than doubled year over year in the first half of 2022, and the company looks on track to generate record FCF for the full year. That alone makes ExxonMobil one of the best oil stocks you'd want to add to your portfolio right now.