I work in a small restaurant with a cash register for check out (i.e. I do not carry my own bank). As servers, we are held responsible for any patron checks that are not closed at the end of our shift. This could be due to a patron walking out or the cashier not closing the check. The cashiers in reality could pocket money and leave us as servers responsible for paying checks. Is this legal practice? We are a very busy restaurant and it is impossible, when I give a patron their check, to keep tabs on whether they pay or not. I usually do not even work near the cash register.

If you are asking whether the walk-out check amount can be deducted from your paycheck, the answer is no, not without your written authorization, specific to the instance in question.
http://www.dllr.state.md.us/labor/wagepay/wpdeductions.htm

My employer takes it from our tips. We are not allowed to leave/clock out until we pay it from our tips. I guess he considers it damages that I have caused by a customer not paying.

That's just a subterfuge. Your cash tips are yours and are not subject to forfeiture. Contact the state Dept. of Labor.