I am trying to work out if I have got this mod set up right as I believe the tax calculation to be a bit odd.

I can get the set up so that the VAT shows correctly but the discount shows up wrong or I can get the discount to show correctly but the tax then for the order is wrong.

I have been testing this again and again and seem to have a discrepancy with the way tax is calculated. Have I got something wrong.

To simplify this I have got 2 products the same price and set better together to discount the second by 5% UK Vat is 17.5% so:

Sale Price £29.99
Discount @ 5% : £1.50

Sale Price therefore: £28.49

VAT payable is £4.47 on the £29.99 item And VAT on second item is £4.24 i.e on £28.49

Total VAT is £8.71

However I get £8.67 showing in Zencart.

The set up for this is INclude tax true tax calculation - Standard

If I change this to include tax false then the discount is £1.28 but the tax calculates correctly to £8.71.

How is the tax being calculated when the better together module is in place as I cannot get to that figure?