Pardon me for going into the whole tipping thing... I'm one of those server people you mentioned
Whereas I definitely share meals in restaurants, drink water rather than pop, and usually eat cheaper cuisine, I tip mostly between 20 and 25% (us servers have a certain admiration for others in our position), and always on the grand total. If most people dont know they are only required to tip on the subtotal, why would the server? This is definitely the first time it's been pointed out to me. If someone tipped me say, 10% on the subtotal, that would register well below for the grand total, and I'd feel pretty crappy about it. Of course, I dont feel too great about 10% either, but at least it's 10% and not 8%. I dont think anyone should tip any lower than 15% if the server does a good job, and still 15% on a subtotal would register lower to anyone unknowing of this idea of tipping on the subtotal. It's a touchy subject, but as someone who's entire income is left solely to others' generosity (or the wolves, as it sometimes would seem), I can honestly say that that extra couple bucks you spend on a tip factoring in the tax can make or break someone's day. Take my word for it.