What struck me was that she had apparently never tried giving change by counting up. Some of you may be shaking your heads at this point, especially if you ever worked a cash register in your youth. But perhaps by now you have kids of your own.
The correct answer is who cares? Well, the customer cares,
and the manager cares, but you don't. Counting up is a way to give
correct change without actually bothering to figure out how much it is.
Notice that you've pulled out three bucks, which is exactly how much you owe me. You could've figured out that you owed me $3, then counted out "one, two, three," but you get the same result if you just count "eight, nine, ten."
But people's totals don't usually come out to nice, round numbers. More often you'll wind up with a total of $11.43 out of $50. Not a problem. You just count out pennies until you get to a multiple of five cents. Then you count out nickels until you get to dimes, then quarters, dollars, five dollars, and so forth.
So let's say the total comes to $32.33 and the customer hands you $50. Start by counting out pennies: "34 (pull out a penny), 35 (pull out a penny)."
Since 35 cents is divisible by 5, move on to nickels. Starting from 35 where you left off, count out "40 (pull out a nickel)."
40 is divisible by 10, so you can move on to dimes: "50 (pull out a dime)."
50 is divisible by 25, so you move on to quarters: "75 (pull out a quarter), 33 dollars (pull out a quarter)" (remember, you were counting up from $32 all this time, so when you go up from 75 cents, you're really going up from $32.75 to $33).
Now continue with dollar bills: "34 (pull out a dollar), 35 (pull out a dollar)."
35 is divisible by 5, so you continue with five-dollar bills: "40 (pull out a fiver)." Then ten-dollar bills: "50 (pull out a tenner)."
Now, 50 is divisible by both 5 (nickels) and 10 (dimes), but it's also divisible by 25. So skip the nickels and dimes, and go directly to quarters: "75 (quarter), one dollar (quarter)."