Consider the story of a Canadian woman who purchased a product on-line from a well-known catalog company.  On its site she was told that $25.00 is added to every order from Canada and that all duties and taxes are the customers responsibility.  Now most people would be deterred by such a comment and simply not order at all.  This however was my wife and she was determined.   She ordered the goods and was whacked with a terrible exchange rate to Canadian dollars.  She had to pay an extra C$13.27 for duties and to top it off had to hand the UPS driver an extra $8.50 for taxes.  Thank heavens it fit and she didn't have to return it.  

Expand your market.  Most non-US customers are deterred by this nightmare.  This scenario locks most US based internet sellers into the US market and they forgo the potential of a 10% increase simply by making their fulfillment Canada friendly, let alone friendly for the rest of the world.  Customers do not want to deal with customs and they do not want to worry about returns.  They want to purchase in their own currency within the custom boundaries of their country.

Your products cost less!  Product shipped in bulk are dutiable at wholesaler's purchase cost, rather than customer's full retail value. Why make the courier companies rich, courier costs in local countries are cheaper than international rates.  Pass these savings onto the customer, bulk shipments add nominal costs to the individual items. 

Your customers are happier! ; They know you and trust you. They are paying in Canadian dollars, they don't have to worry about customs, they know they are being sent from within Canada and the know the have someone in Canada to deal with.

Your customers buy more!