I think you should count the change back yourself, as the kids that get these menial jobs are not maths geniuses.They may have been more on the ball in the olden days when there were not as many opportunities for bright kids to get ahead and do something more suitable to their abilities. Now it is different knowledge that they deal with. I think it is wise to help out those of lesser ability by putting in systems that help them to cope as not all of us have average intelligence.