Need Tax amount to be fixed not depends on the unit price

Dear All,

We have a question on tax amount. Our issue is that we need to assign a specific flat dollar amount based on the quantity of a line item and not a percentage rate. The system seems to only let us enter a percentage when setting up the tax codes. For example: if we have two customers receiving XYZ product, one at $10.00 and one at 15.00, we need to be able to charge both of them only $1.25 based on a quantity of one each rather than on the price of the product. Therefore, if the quantity on the item went up to 2 the tax(fee) would automatically increase to $2.50 based on ($1.25 x 2). Any suggestions? Thanks.

Regards,

Yuka