Calculate sales tax before discount amount in ax 2012 R3.


I want to calculate sales tax on the whole amount not on the discounted amount. Is it possible in AX 2012. 

Let me explain I have a item with 100 RS and discount on this item is 10 RS now net amount is 90 RS Sales tax will be calculate on 90 RS.

But we need to calculate on 100 RS before Discount amount is it possible in ax 2012, if not please guide me how to customization this requirement. 

Thanks in advance.