I love those Australia issues too. I do not have enough of them to suit me.

Bee See, Canada does not charge HST or GST when you are paying to ship internationally (outside of Canada) that the postage is over $5.00 on (which is all parcels and packets).
However, if you were to go in and just buy the stamps separately that added up to the parcel price you would be charged GST and HST or PST on them (13% in Nova Scotia going up to 15% July 1, Canada Day, woo hoo, wave the Flag day.) It's just when you actually ship to international, either online of in person, that you get the tax break.
So buying a $1.70 stamp to mail a letter internationally would cost $1.70 plus 13% tax right now (May 16, 2010). If I bought 3 of them ($5.10 + tax) I would still pay tax. Only if I wanted to buy and use them immediately (please ask, labels are used as default) to pay the postage on an international (or USA) shipment would I not pay tax.
So, using the stamps I have already, on a parcel I want to mail outside Canada is costing me money because I paid the tax on them when I bought them as just stamps years ago.

But I get to make up some neat looking parcels though.
