It's not really in dispute any more:
Sam Stein: Could you set the record straight about the tip? Your manager says they left something but you contend it never happened.
Anita Esterday: If your phone is ringing from six in the morning till four in the afternoon and customers are saying what's wrong, the telephone lines are down, and it's because reporters are trying to get through, you say whatever you have to say [to get them to go away]. I don't know if they left a $100 tip or not but I haven't seen it yet. And none of the other waitresses have said they got the tip.
But a $100 tip was left, according to the Clinton campaign. The campaign won't say who left it or who received it. That's old news now. They won the news cycle - even against such a right-wing attack operation like NPR. Not a huge deal - but just one of those signs that help you understand the nature of the candidate in question.