Need Help In TAX and Service Charges calculation

I this way i want tax just at “Ticket Total”
For Example

In Picture
Ticket Total: 400
Servicing 5%: 20
Tax Total 10%: 42 ----------- i want here 40

i need tax did not apply on service chrges.

Enable Include Tax setting in Service Calculation but also enable use plain total setting to force it calculate amount from tax excluded amount.