Since that's already what I believe, it wouldn't be a change at all. I must admit though that I didn't tip even when I believed in God, but I was different in a number of ways.

I think the world would change on the margin and that Voltaire was right when he warned of the servants stealing the silverware. The servants might also change their behavior in more desirable ways, but I don't know whether I'd prefer it on net and as it doesn't seem like a likely possibility in the foreseeable future I am content to be ignorant.