The real story here seems to be that somebody at Maid-Rite is chiseling the help out of their tips. From an article in the New York Times:

Reached at her home in Iowa, the waitress, Anita Esterday, said that neither she nor a colleague who helped serve Mrs. Clinton recalled seeing any tip.

She said a local staff member of Mrs. Clinton’s campaign was in the restaurant on Thursday to tell them that the campaign had left a tip. She said that when she and her colleague said they had not seen a tip, the staff member gave each of them $20. Ms. Esterday said she did not understand what all the commotion was about.

“You people are really nuts,” she told a reporter during a phone interview. “There’s kids dying in the war, the price of oil right now — there’s better things in this world to be thinking about than who served Hillary Clinton at Maid-Rite and who got a tip and who didn’t get a tip.”