No matter how often it happens, the inability of many retail clerks to simply make change always strikes me as a telling statement on the pitiful condition of the average American's reasoning abilities. If you can't figure out the simplest of computational problems there isn't much hope that you can figure out much else.
Here are the two latest examples of what has happened on my two most recent attempts to buy lunch:
Today my total bill came to $6.46. I gave the clerk a $10 bill and a penny. I even tried to let her know that I was complicating things with the penny before she keyed my payment into the cash register so that she'd have a chance to avoid the difficult task of figuring this problem out for herself. She got out three $1 bills and two quarters (good so far...) and then started rummaging around in the penny bin. I mentioned that I had given her the penny to avoid getting a wad of pennies, and that I'd rather get a nickel than the five pennies. That prompted her to drop the pennies, dig up a dime and hope for the best. It seemed rather pointless to try to correct her at this point, so I kept the extra five cents as my tip for helping her do her job.
The previous day was an even scarier example. My bill totaled $5.50. I handed the clerk a $10 bill and two quarters. He spent a LOT of time staring at the register, maybe wishing he had keyed in $10.50 rather than just the $10 he had quickly punched in when he saw my bill. One of his helpful co-workers saw the confusion and stepped in to help. The first guy seemed to be trying to figure out how to re-enter my payment so that the register would tell him what to give me, and the other guy told him not to worry about the register, and to just give me my $4.50. As the first guy fumbled around to count out four $1 bills, I mentioned that I'd really rather have a $5 bill, at which point they both pretty much said, "Uh, OK", and handed me a $5 bill.
As a quick reality check I presented the above scenario to my third-grader. He heard the particulars and when I asked what I should have gotten for change he gave a look that clearly meant "Are you kidding me?" and immediately said, "Five dollars."
I realize that I may be a simpleton clerk's nightmare, but I am very patient with them, and I try not to confuse them when there are other customers waiting in line, plus it really doesn't occur to me that I am giving them the functional equivalent of a differential equation to solve.
Still, it never ceases to appall me how often it is so easy to stump someone who should have mastered third-grade math many years ago. I just have to hope that the folks staffing the cash registers are not representative of the average US high school graduate.