In Canada 2 taxes can be charged in some provinces: provincial (PST) and federal (GST).
As a business you register for tax numbers which need to appear on each invoice. When specifying "Canada" and the appropriate province this could be preconfigured.
Several provinces use only 1 tax (HST), others use both.
Furthermore sometimes taxes don't apply to some items / services, and are not required to be charged by businesses making less than a fixed amount of annual revenue. This means when implemented each item on an invoice should have the ability to specify taxes (or not) - issue #54 seems to be about this.
For details, see: