1) if Total Amount is (C)$ and Customer wants to Pays full this (D)$ amount Means We have to apply % Discount on each item 2) if Customer wants to Pay Total amount (tax included) then item price is will be $
Scenario 1 : 3 items in the cart and Gross Total with Tax is $733.34. Customer wants to make a deal and only Pay $700. No you have Laptop on Sale and have no more margin to give more discount on the item #1. so we have to calculate how much discount we have to give on rest of the items. Now first we have to calculate: (A) item #1 with tax ........ $339.99x1.13 = $384.18 (A) (B) Actual Grand Total Amount with Tax ... = - $733.34 (B) .....................................................................========== (C) Now you got the New Total Amount on = $ 349.15 (C) rest of the items (D) we have to calculate the amount he is paying without the item #1 .....................................$700 - (A) $384.18 = $315.82 (D) NOW PUT THE C AND D VALUE IN EQUATION 1 TO GET THE DISCOUNT PERCENTAGE FOR REST OF THE ITEMS