Myntra coupons are like this from the start. There are items on their website where applying a coupon will not add the tax component but you have to hit and try and i know it will take a lot of time.
So my suggestion is that in case if you want to purchase some product then put it into your wish list and wait for a coupon or sale like on every Wednesday. Apply the coupon and see the result. If you are not satisfied with the discount then wait for the next sale or special event. I know it is little tedious to wait for a product like this but i can assure you that you will someday get some coupon which will not add that nasty tax component. I have tried the same many times. The only thing is that it requires patience.