Random Questions; Random Days.... Monday May 19

Let's say you stopped at a party store for a quick purchase. You gave the clerk a $10.00, but the clerk gave you change for a $20.00. You are aware of the error as soon as the clerk counts back your change. What do you do?

I would give the 10 bucks back to the clerk. I'd hope that if the roles were reversed, the customer would do the same. It has happened that I've gotten back to my car and realized that I was given the incorrect change. If it was a considerable amount of $ I'd go back in and return it, or if I was shorted, I'd go back in. If it was a few cents off, either way, I'd let it go.
O&O!!!