Cart displaying strange values when used coupon/voucher + Paypal Problem

[encoremj]

When I'm using voucher for example with free shipping and 15% discount my cart behaves strange.

Small cart shows everything fine: 29.99 product - 4.50 discount (picture 1)

But shopping cart summary shows different values - 29.99 product - 7.49 (4.5+2.99) and still shows total shipping 2.99. At the end of the day total amount is all right but it looks bad, some customers still may think that they are charged p&p (especially when they order more products)

Paypal see everything like on picture 2.

Problem pops in when product is cheaper than 2.99 and I'm still using that voucher. (totals shown on picture 3), and paypal reports error (pic4). From my point of view presta substract 2.99 from product price and not from shipping cost. That's why paypal report error when product is cheaper than 2.99 (1.20-2.99= -1.79) +2.99 shipping = 1.20 but that minus is probabily problematic.

Anybody has any solution? Thanks