I lived in Ottawa for 7 years and crossed into the states via various routes frequently. The customs guys were frequently amused by my importation of maple syrup and large blocks of aged cheddar. They are never amused when they are on some sort of alert.
A friend, antique dealer, once spent a nasty three days chain smoking in a very small room until they were absolutely sure he was not the terrorist on their watch list. Both US and Canadian customs were involved in this deal. I suggest that you just tell them that you are mileage running.