As we become more and more dependant on computers, we become more at their mercy when they malfunction. If we all paid cash, there would be no problems.
Back in the day that I worked in the grocery store, when someone bitched about their ATM/Credit cards not working, and blamed me for it, I would calmly tell them that if they paid cash, they wouldn't have to worry about it (for the record, I never saw our ATMs in the checkstand go down, but it always seemed to be OUR fault).
The kids that work the registers aren't taught and don't have the common sense to figure out what to do if their computer doesn't work. This is commonly referred to as the "dumbing down of society". The new programs on the registers don't tell the kids to give you back $15.86, they tell them to give back 1-$10 + 1-$5 + 3-25c + 1-10c + 1-1c. With pictures, in case they forget what a quarter looks like. That is why when you say, "Oh, wait! I have the 14 cents", they look at you like you just asked them to explain the theory of relativity in a 5 paragraph essay. They do not know to add 14 cents to the 86 cents and you get $1 even. We have made them idiots.
How true that is..sadly.
Weird thing is if you give them the change before they punch it into the register they still look at you like you're crazy.. I've had them give me back the small change I gave them to make it an even dollar and say here you gave me too much....then proceed to take the cash and give me even more small change I didn't need in my pocket.