Legality of owners taking deductions off paycheck in Birmingham, Alabama

Hi, I am A server at a locally owned Chinese restaurant. Pretty regularly the owners will "punish" us for not doing a good enough job by taking money off our paychecks. Our base pay is only 25 dollars for a full 12 hour shift (with no breaks). I generally end up making around 16 an hour here after tips, but these deductions are making me worried. My friend just had 42 dollars taken off his paycheck for "forgetting to charge for wine, even though the customer hadn't tried to pay yet. What is the legality of this? I'm in Birmingham, Al.