Essentially the boss has not legal bases to take your tips because it's a form of income and there for you will be taxed on it just like any other. Like they said above I would file a claim/ and / or get a lawyer involved because the owner most likely not claiming the tips and there for not paying taxes. In the end you earned the tips fair and square.
Another thing to mention is because you use square I'm pre assuming that you have your own login and there for when you get tipped it gets collected and taxed end of the year on your W4.
I'm no lawyer but this would be the best course of action due to the fact I work for the world's biggest pizza chain. Hope this helped!