This should not affect getting the job. Get and keep a copy of the order dismissing your case. Also, you can expunge the record as well.
First of all, it's just an arrest now. Second, if it's the prosecutor's MTD, you should be golden. In some States "Attached Tags Not Assigned" is actually an anti-theft, anti-chop shop measure and can be a felony, so make sure the dismissal actually goes through. Sounds like you're in good shape though. Good luck in the new gig.