Canadian Zip Code matching for GST

[mltsy]

I am trying to add 6% GST for Canada, but for the tax calculation, there seems to be no way to match Canadian Zip codes - or anything other than 5-digit US zip codes for that matter. Is this possible? If not, perhaps the zip code matching should be changed to use (or give the option to use) regular expressions rather than whatever it's using currently?

Is there another way to add GST?

Thanks!