You wouldn’t believe how easy it is for old people to rip off younguns at a cash register who can’t make change without a machine to tell them how much.
I think most at the cash register are pretty dumb, regardless of age. I have had both young and old cashiers confused when I handed them cash that included change. They far prefer automated forms of payment (credit, debit, etc.), but if you hand them cash then it had better damn well be either exact or just a few big bills.