My sister and I order from US stores frequently. I got hit with duty once. Her... never!
I think I paid another $30.00 on an order that was already $30.00 postage and handling. So I got $70.00 of reasonably priced fabric for $130.00.
I think if your order is valued at less than $60.00, it escapes customs. I fyou contact Canada Post they might have more information for you.
Lori