Excellent Mod. Belated thanks, I know it's been around for a while. I'm not really sure if this mod is stillbeing supported but I've been testing it against 1.38a and with some of the manual edits detailed in this thread it seems to be working ok.
If anyone is using it, I did find one bug with the addition of postage costs. The script finds the total postage price, counts the "different" products in each order and then at a later stage divides the total postage price by the number of products in the order.
The problem I found is with having more than 1 of the same product. It doesn't take this into account in the postage calculation(ref Line 144):
$count=$count+1;
This means that if you have 2 of the same product the overall count is only increased by 1. The result is that you'll have additional postage costs in your net total.
I've changed line 144 to:
$count=$count+($Orderedproduct->fields['products_quantity']);
and this seems to cater for this. Not sure if there are any other impacts of making this change yet, but If you're suffering from order total mismatches. Take a look.