How do I change the Order Total Calculation.

[zaps]

I use the OScommerce MS2 and Currently my Order Total looks like this :

 

 

Sub-Total: $9.95

Packaging & Delivery (($3.95 first item, $2.95 each additional)): $3.95

GST @12.5%: $1.24

Total: $15.14

 

The Order total does not calculate the tax on the freight and add it to the Total order value.

 

Instead it should be : ( Here, tax is charged on the freight charge also)

 

Sub-Total: $9.95

Packaging & Delivery (($3.95 first item, $2.95 each additional)): $3.95

GST @12.5%: $1.73 ( this is Total / 9 )

Total: $15.63 ( GST on the Packaging & Delivery should be added to the total )

 

How do I do that ?

 

Can somebody please help me in this.

 

Thanks in advance.