Doug Orleans's Journal

I did a lot of this on the trip, but not always. I noticed myself applying some quick heuristics in which I estimated the intelligence of the cashier, the intelligence of the cash register, and the dependence of the former on the latter to do math. Some people are smart enough to understand what you're trying to do; other people aren't, but they just punch in the numbers and give you the amount of change the machine tells them to. It's the ones in the middle you've got to watch out for.