How to change where the tax is calculated?

[LarryLarryLarry]

Hello, I'm using 1.6.0.11.

How can I change this:

( price x tax ) x quantity

to this?:

( price x quantity ) x tax

 

Alternatively:

I notice that the system discard the trailing decimal numbers, how do I make it that it does not cull the trailing number in the first calculation, that way the price will be correct even if it calculates ( price x tax ) first.