And to follow that up...last week I took my parents on a bus ride home after they dropped their hire car off.

I now carry a bag of $1 and $2 coins (to avoid the embarrassment mentioned above) and I filled the bus driver's little tray until his cup runneth over with what I hoped was the correct change. He heaved a great sigh and just started shoving it in his coin tray. I said "let me know if I haven't got it right".

The response? A very surly "Well I'm going to have to trust you. I'm not counting all that."

I believe the lesson is that you just can't win.