Discount problem

I am facing a problem. This is my ticket

Ticket Total is 1397.00 and GST Tax is 223.52 Now Total payed amount is 1620.52

Now i am going to give 5% Discount

I apply 5% discount. The problem is that it apply 5% discount only on Total amount not on GST Tax.
I want discount including GST amount. I mean GST should also reduce. How i can achieve this???

How are you currently calculating the tax?

Try reordering the calculations, not sure if will help…

Alternativly changing from a auto calculation to having an update calculation action on a ticket total changed rule using a formula.

i am using calculation type to calculate Tax

Yes, get that but with what settings?
If you make it using an update calculation action you can set the discount amount on ticket total update using a formula rather than a fixed 16%