Calculation inclusive of vat

how to show and calculated  in inclusive vat in  base amount for exampal if per product price in 500 taka tow product sase 500+500=1000 discount 200 than case amoun 800 this amount 800 is base amount  I want this 800 taka inclusive VAT 5% bilow this example The black mark here is just right on a product. I want to do this calculation on the red circle below. How can I do that