Ability to create a Tax Classification code that Exempts (GST and PST) at the transaction level

Hello,

We have a need to exempt imported sales order of taxes.

All these transactions have the shipTo country as Canada.

We need a 'Tax Classification Code' that exempts the GST and PST.

The tax classification code seems to ONLY exempt one type of tax (either GST or PST). We need to exempt GST and PST.

So the question is : How can a Tax Classification Code be set up that exempts 2 types (GST and PST) of taxes.

Wondering, if any of you know how to make it work?

Regards

Rahul