Can my employer deduct money for any reason that he sees fit?

Question Details:

I work for a dentist who constantly states that he will deduct money from our checks. My husband got into an argument with my boss who kept me off the clock with my 2 year-old son because he said that I had to do a performance review without pay for 2 1/2 hours. He took my key away for this incident and told me that I wasn't being fired, but that he was changing the locks and deducting it from my pay. Also, he has threatened to take money that patients fail to pay for treatment out of our pay. He says that this is legal and that restaurants can do it if someone leaves without paying. Is it legal? Important Notice