We use an ERP system that calculates VAT line by line for each product. Whereas nop calculates the VAT using the subtotal. Normally this isn't an issue and the VAT lines up with our ERP system when the nop order is sent to the ERP system. However there has been multiple orders where the VAT is out by a couple of pence, sometimes jus £0.01, other times as much as £0.03. This can and will cause issues down the line. I have done the calculations and seen why the line by line is this different compared to subtotal calculation.

Now I partially have access to the source code (takes a long time for our 3rd party host to contact me and send me relevant files that I need). I have also searched the forums tirelessly and have not found any answers to my problem. Is there a way to make it so that nopCommerce calculates the VAT 'line by line' aka product by product instead of via the subtotal?

Below is an example of why this issue happens -

NopCommerce Order -

1 X ItemA @ £286.37 Each = £286.37 Excl VAT
1 X ItemB @ £286.37 Each = £286.37 Excl VAT
1 X ItemC @ £45.17 Each = £45.17 Excl VAT
1 X ItemD @ £13.12 Each = £13.12 Excl VAT
1 X ItemE @ £9.91 Each = £9.91 Excl VAT
26 X ItemF @ £9.57 Each = £248.82 Excl VAT
52 X ItemG @ £4.21 Each = £218.92 Excl VAT
1 X ItemH @ £15.00 Each = £15.00 Excl VAT

Sub Total = £1,123.68 then it adds VAT (20%) which = £224.736 (Rounded makes it £224.74)

This makes Total = £1,348.42

All well and good until it goes to our ERP system, where it calculates VAT for each product, rounds it then moves onto next product/line.

ERP Order -

1 X ItemA @ £286.37 Each = £286.37 Excl VAT then Calculate VAT = £57.274 (Rounded = £57.27)
1 X ItemB @ £286.37 Each = £286.37 Excl VAT then Calculate VAT = £57.274 (Rounded = £57.27)
1 X ItemC @ £45.17 Each = £45.17 Excl VAT then Calculate VAT = £9.034 (Rounded = £9.03)
1 X ItemD @ £13.12 Each = £13.12 Excl VAT then Calculate VAT = £2.624 (Rounded = £2.62)
1 X ItemE @ £9.91 Each = £9.91 Excl VAT then Calculate VAT = £1.982 (Rounded = £1.98)
26 X ItemF @ £9.57 Each = £248.82 Excl VAT then Calculate VAT = £49.764 (Rounded = £49.76)
52 X ItemG @ £4.21 Each = £218.92 Excl VAT then Calculate VAT = £43.784 (Rounded = £43.78)
1 X ItemH @ £15.00 Each = £15.00 Excl VAT then Calculate VAT = £3.00

Total with each rounded VAT added = £1,348.39

For us, the nop calculation must be made to match the ERP, not for the ERP to match nop due to how it is operated.

If anyone knows of anything or is able to help it will be much appreciated as I have been on this issue for about 15 days now.

TIA