Using Classic Outlook on Windows for personal email, calendar, and contact management
Yes, an F3 will work if you are web-based only. This is typical when using Kiosk computers. To configure a computer in Kiosk mode see;
Configure kiosks and digital signs on Windows 10/11 desktop editions - Configure Windows | Microsoft Learn
The user can then login to Outlook using a web browser.
There are a variety of possibilities as to which account type is used for the Windows computer itself. See the documentation in the link above for more info.
You can also offer a shared computer to which they login with their own credentials. Then the use of Outlook for Desktop is possible as well (since each user can store their own settings within Windows) and the use of device-based licensing is then recommended.
Another way to go would be to provide mobile devices instead of stationary computers. This can be a good choice when your floor personell roams through the entire shop and can make sales as well. Then you wouldn't directly need a "classic" check out desk either. The Apple Store is a good example of that.
There are lots of possibilities, but which exact once you should choose depends on your working scenario. Credential sharing is not one of the possibilities which you should consider ;-)