Had an experience at a rare lunch out with my husband today and would love to hear others' opinions about this. Went to the Friendly Toast in Portsmouth, NH, which has good food and uneven service of the tattooed hipster variety (N.B.: My stepson is tattooed and pierced, but since he lives in San Francisco he tends to save the attitude for those who give it to him first-- not so in the hinterlands of New England, alas). The bill was $29.90 (Portsmouth has gone from hippe haven to yuppie mecca over the past 15 years) and I put down $40 in the form of two $20's. The server, who had a total of three tables (it was late afternoon and the place was deserted) asked me if I wanted change. This really irked me. I suppose it's possible she had forgotten the total of the bill she had added up a few minutes before, but when I waited tables (admittedly this was only for a few summers and two decades ago) I never did this because it seems so presumptuous. Isn't it up to the customer to determine how much and whether they will tip you? And why would anyone assume that a $10 tip was in order for a $30 tab? We were polite, we didn't ask for substitutions, she was on shift and you'd think a hungry couple in the middle of the afternoon would be welcomed business. As it is, I left her $5.00 voluntarily. She stiffed me on the dime, so the total tip was $5.10. Not my customary 20%, but not punitive, by any means.
So, to repeat, thoughts about when or whether it's okay for a server to ask a customer if they need change? And note that in cases when I actually don't need change, I am careful to say clearly: "We're all set here, have a nice day".