who literally did not know the difference between a nickel and a dime. I told her and showed her that she gave me a quarter and two nickels but it should be a quarter and two dimes. She had a puzzled look so I held up one of the nickels and said, "this is a nickel". She asked, "that's a nickel?" And off she went for some help. I probably would have let it go at that point - just 10 cents - but for some reason, I guess I felt sorry for her and I like the business. It didn't ruin my day or anything but it was surprising. Math errors when making change don't seem uncommon these days but this was a first for the cashier not knowing the denominations.