Why do you need to be a cashier to use a number pad? I use it even when I just need to enter a zip code or a credit card number...And all of these people are professional cashier typer types??
I grew up with ZX Spectrum & co. and today much faster with the regular number row than 99% of the people I know that type on a numeric pad. Your post is Frost-bait, nothing else.
[To paraphrase a former boss of mine, "Just because Frost said it, doesn't mean it's wrong."]