NWIND design: calc taxes?

[DLB]

Hi All,
My app works similar to NWIND, in that the calculations for Extended Price
[OrderDetails subform] is purposely saved to a table. It is easy enough to
calculate taxes based on a sub-total, but what design or method would best
capture the sub-total, the taxes and finally the combined total cost? (This
requires multilple different state/provincial/federal taxes.) I'm assuming
the taxes are also a component of the OrderDetails items. Any thoughts?

Thanks for any assistance!