It may be valuable to note that certain items made in the USA, Mexico, Chile and Costa Rica are not subject to customs tariffs.  I am still reading through the specific schedules to find a reference but here is the documentation and couple places to check out. 

THIS DOES NOT APPLY TO HST/GST - that is a federal sales tax that should be paid on all purchases that are not exempt (like some food items like milk or a cake that serves 6 or more)

Ad supported site that talks about cross boarder shopping: http://www.crossbordershopping.ca/duty-tax-import-guide/duty-tax-tips
Canada Revenue Agency Landing page for Tariffs: http://www.cbsa-asfc.gc.ca/trade-commerce/tariff-tarif/2008/01-99/tblmod-1-eng.html
Section of the Tariff schedule that applies to electronics: http://www.cbsa-asfc.gc.ca/trade-commerce/tariff-tarif/2008/t2008-01/ch85-eng.pdf

I learned about this last year when I was looking into buying a metal lathe.  Lathes and other metal working equipment can be tariff free if made in the USA, Mexico, Chile or Costa Rica.