Random discount => tip situation?

[jba]

in this situation I would also have paid $10. basically when something like this happens I will usually pay at least what my check would have been, and look at it as I just saved the tip. unless it is outrageous, then I usually split the winnings with the server. for example if you'd order $20 worth of shakes and she rang you up for $5 I would have left 12-13.