I'm having a problem with my cart perhaps you can help me?

I have a 10% coupon for customers to use when they buy something for the first time at the online store. They enter the code in the cart. Go to the confirm order page and its reflected with the 10% price.

Then they go to checkout in Paypal but the price shown in Paypal is the original price without the 10% discount.

When they pay, the correct amount is charged and it is correct on their receipt.

What's up with that? How can I fix it?