order tax not calculating correctly

[etoile03]

i'm not sure what i have set up incorrectly, but my order is not calculating correctly. the tax is off. i have free shipping for orders over $150 set up under order total > shipping. i also have a 10% discount code for any orders. (The tax seems to perform correctly when no discount code is applied)

Sub-Total: $260.00
Discount Coupon: test : -$26.00
Shipping:$0.00
TX TAX 8.25%: $17.16
Total:$251.16

Here is the sort order for the order total modules:
COD Fee ot_cod_fee Info
Discount Coupon ot_coupon 280 Info
Group Discount ot_group_pricing 290 Info
Gift Certificates ot_gv 840 Info
Low Order Fee ot_loworderfee 400 Info
Shipping ot_shipping 291
Sub-Total ot_subtotal 100 Info
Tax ot_tax 300 Info
Total ot_total 999 Info

[etoile03]

anyone have any ideas?