When I don't feel like dealing with the hassle of extra change (mainly coins), I tell the clerk to "keep the change".
I sometimes think this can be taken as an insult, instead of a positive way of expressing good service. You're telling the person to keep 89 cents, as if they need that.
What do you guys think? And for any of you who work, when a customer tells you "keep the change" how do you feel/react?
"You need this more than I do", is what I picture when I tell a clerk "keep the change". But, I don't mean that at all, I just don't want the change.