US Sales Tax Amount Limit

Hello,

I got a request from a customer in the US to create an 80$ limit for tax amount calculated out of tax code U1 which is 1% sales tax.

For example if i have an invoice for 10K then the sales tax will be 80 and not 100.

any idea of a user exit i can use or another procedure to be able to dothis.

Thanks,

Arnon.