This isn't legal advice, it's just my opinion based on what is on the PA Dept. of Labor and Industry page says regarding minimum wage & people who earn tips. It does look to be an illegal practice. Here's the website so you can read all about this yourself. At the bottom of the page there are phone numbers for the Bureau of Labor Compliance offices around the state. You may want to contact an attorney near you for legal advice before you do anything. You have to decide what action you want to take, if any, and also think about looking for a job where you are treated fairly, if you have a choice in your vicinity. Good luck to you.
If my answer was helpful to you, I would appreciate if you would mark it either "helpful" or "best answer" if you feel that applies, as AVVO gives us rating points based on feedback. Thank you! Please note that the above answer is not to be construed as legal advice. It is my personal opinion based on your question, and it was given without obtaining the detailed information that I would normally request in order to render comprehensive legal advice. I advise you to consult with a local attorney of your choosing to obtain specific legal advice. The fact that I answered your question does not create an attorney-client relationship between you and me.