When a customer hands me cash for their purchase, I state the purchase amount and the amount of cash, ie: $24.95 out of $30.00. This way the customer knows I'm paying attention and I have impressed my mind with the amount. Then I count the change due back. When I'm the customer, I count my change if the clerk doesn't. As others pointed out, many young people aren't being taught to think, just look at what the register says.