Opencart - Make a VQMod of Tax Module

Need someone to develop a new Tax Module on Opencart, using VQMOD. This tax module will display as a calculation and won't affect on the Order Total that customer should pay, so it's not the same as default Opencart tax module. Tax name: Goods & Service Tax Display as: GST (inclu. 6%). Refer our attached file on how it should display in front-end. The calculation of this tax should be (Subtotal - Discount) x 6%. Shipping fee should not be taken into calculation. Example: 3 products total $100, Coupon discount - 20 = Subtotal is $80 So it should display GST (inclu. 6%): $4.8 This row of item should display in Checkout, Cart, Admin Order Details, Invoice and Reports. The style should fit together with the theme, but this shouldn't be a problem as long as you don't change anything on the CSS. *IMPORTANT* Your mod must compatible with all the extensions that are currently in the store. The store is live so your code must not have any bug or cause any error! We have a special promotion module so your code must also works with it.