I plan to pack some nonperishables to bring with us, any problem with open packages coming across the border? Most of the stuff will be new, and unopened, but things like tea bags, cereal, etc may just be in ziplocks. I just want to bring a few things that we can use up while we are there; I don't like the idea of buying it down there and then having to leave nearly full containers behind because we ran out of room in the luggage!