Virginia charges $5 for non-commercial use, $10 for commercial (rentals). The State Dept. Of Aviation are good guys, I don't begrudge them the $5.
Failing to register with them doesn't seem to have any enforcement, further not registering will not keep you from escaping the state tax department that combs the FAA registration database to send sales tax bills (whether or not you actually already paid the sales tax) nor the county property tax people who just comb the local airports (including looking into hangars) for based airplanes.