>I don't think that is possible - due to rounding scenarios
>
>Take this for example
>
>

>Provincial tax on  $1.74 is round(1.74 * .095, 2) or $0.17
>
>What amount is the base of $0.17 tax ?
>
>round($.017 / .095,2)  = $1.79  (see how this compares to the original $1.74)
>

>
>iow, you need the Total including all taxes, and knowing the two percentages and the order in which they were applied, you work your way back

This is what I think too but I will take a look at the other message you provided.