Another way to avoid customs issues (and exorbenant shipping charges) is to order items, when available, from a company within your country's borders.

I can't speak to Canadian Customs (and for Canadian Companies), but we absorb all shipping costs from Scotland and all US Customs fees. Prices we quote our customers on our site are actual 'to your door' prices, many times with free shipping (on orders over $200) and mostly 'tax free' (ALL states except PA, where we only charge tax on applicable items). No surprises = happier customers.

Just my $.02