Is it legal to not pay hourly employees for the hours they've worked past 30 min after closing if they aren't done and still working off the clock?

I work at a Subway franchise in Chesapeake Virginia and they said if we're not done with our closing duties by 30 min after closing that we are not to be paid for the rest of the time it takes us to close. They have sorted my check 3 times, twice due to this, they've changed records in their computer to coincide with the actual pay I've received that does not match my time slips. They have a terrible habit for years of not paying employees their rightful hours worked. I have records of this though I doubt anyone else does. They also do not pay overtime. They made us sign something that says we're to reimburse the register if it's short and that is the equivalent of not paying us our full wage per hour. They take advantage of us and they won't pay for another employee's injury that occurred in their store. They asked her to fraudulently claim it on her Medicaid. Now they are talking about firing me because I am trying to file a complaint with the dept of labor. This is all illegal right