I would put together a log (along with your video evidence) of every date, time, etc., it happens. Then after you have a couple weeks worth of entries, ask to speak to the manager. If they appear to dismiss it, turn your phone on, record the encounter, and press the issue, by pointing out how it is short changing you and you plan to call the owner (if it is a franchise) or corporate.
Because this is fraud, even if it is just a few cents. It adds up, and for sure you aren't the only one it is happening to. I'd be irate.