I'm surprised they have not made you pay the additional taxes.

They did this to me, except that the additional taxes on one ticket were more than the other, despite the itineraries being the exact same (booked thru different AP accounts, at the same time). The taxes charged initially were the same, then they added more taxes in later on, of course they were different amounts.

I question whether AP knows what they are doing at all, as they were unable to give me an explanation when I asked about the difference.