I'm running into a rounding issue when parsing magento orders to invoices out of my ERP system to be inclusive of the discount. Is there a way I can configure the coupon discount to be calculated against the unit Price and then multiplied out by qty.

Eg Magento sends this.

MyProduct x 390 units @ $1.55 = $604.50 less 15% (90.675)

= $513.825 total value

MyProduct = $1.3175 each

but it hits my ERP system it gets rounded to $1.32 and then total value goes to $514.80…..

I think this is because For the discount, Magento is using total line price $604.50 x 15 % = $90.68

Not unit price - $1.55 x 15% = $0.23 X 390 = $89.70……if we get $89.70 then that will work for EDI in our ERP,

ie we can calculate the Unit Price as TotalPrice/Qty …….$514.80/390 = $1.32 unit price

I hope this makes sense, Any ideas of