Here is the updated link for the Nashville, Tn Law just be aware other municipalities can have a different one, and the Nashivlle law is very old and very vague.
Best thing to do is get a Ham Radio License and most states allow for you to operate a scanner in a vehicle.
Also the old rule of thumb still stands as previously stated out of sight out of mind.
Do a search of this forum there are other thread to this also.
They won't bother you in Tennessee. Go to Kentucky and they will confiscate your brand new Pro-96 and give it to their kids if you have it in your car.