here ya go:
http://www.cjrpc.com/interstate_1.htm
when your done reading this you will be better informed than a lot of highway patrol and state police you may encounter
kraigwy makes a great point - even if your complying with the law you may have your trip delayed in a way you dont want it to be.
why push the issue?? unless you like playing dimestore attorney with the local magistrate or police supervisor.
common sense says don't take a chance and leave your high caps at home.
if your really really really worried about getting into a sustained gunfight then get a few ten round mags and go practice your mag changes