I created a discount from the admin/promotions/discounts and add new discount. Then, I did a test purchase and went through checkout. In the checkout page, I put in the discount code and then apply discount. After going through checkout and passing to paypal sandbox, the difference will be seen (just remember to copy down the amounts on the nopcommerce side and compare it to the paypal side).
Thanks for checking into it.
I fixed it... sort of... there STILL could be a one cent difference! I have to figure out why... then it will be truly fixed. There is just a slight difference in rounding between nopCommerce and Paypal. Damn! I could end up being on penny less in Paypal (possibly one penny more - not sure yet).
The way that nopCommerce does discounts and tax is that is takes everything in the cart and figures tax... then it takes the disount off... leaving the customer having to pay tax for the discount. That doesn't seem right to me. I've tried to factor in the discount when the tax is totaled, but the rounding is off just a hair....
The fix I have has several changes in ShoppingCartManager, OrderManager, TaxManager, and a module OrderTotals.ascx....
I'm sure this is not the way that Andrei would do it, but it (almost) works. If I can just get that penny!
I'll let you know when I'm finished. I'm VERY close. It all depends on how nopCommerce rounds as compared to Paypal. Sometimes the total matches EXACTLY... but then sometimes the rounding makes that penny difference.