Canada Import Tax

I can't figure how to setup the Canadian Import Tax on a foreign invoice.  There are two scenarios 1: the duty percentage is the same for all items in the invoice.  2.  The duty percentage changes based on the line item of the invoice.

For #1, I tried to follow the example described in the wiki, but it doesn't seem to work.  The import tax needs to be calculated first and then apply the provincial/federal tax.
Let's say invoice $1000.00: Import Tax 5%, so the total of the invoice for tax purpose is $1050.  Now, we apply the provincial/federal tax on top of it, so $1050 + 13% = 1186.50.

#2 is a more complex scenario where each item can have a different Import tax, so let's say item #1 pays 5% duty fee, item #2 pays 6%. Then the total should be calculated and only then the federal/provincial tax would be applied.

I appreciate if anybody can help me with this.
thank you
Paulo