How honest are you?

Yesterday at the newsagents I picked up a copy of The New Yorker, the two daily broadsheets and a plastic folder for my references. I gave the cashier twenty dollars. The amount owing came to just over sixteen dollars. In change she gave me back eighteen dollars and some cents. As I was talking to her about subscribing to the newspapers — I buy them almost every day from the same place and she knows my face — I looked at the change in my hand, before putting it into my open wallet. Guilt? Not much. I guess these little windfalls don't come very often. But now that I think about it it reminds me of the time in Japan that I found three thousand yen on the pavement. Of course I picked them up and put them away in my wallet. My wallet is a different one now, but my evil tendencies are the same.

What would you have done?