Checkout Header Price Discrepancy (Net vs Gross)

The checkout header is incorrectly mixing net (tax-exclusive) and gross (tax-inclusive) values. It subtracts a gross discount from a net subtotal ($239.67 net - $159.50 gross discount = $80.17), resulting in an incorrect discounted price display in the header. The user expects to see gross values ($290 and $130.50). The subtotal section correctly calculates the total as $130.50, but the header discrepancy is causing customer confusion.