Sales and Use Tax Question

Hello,

Can someone suggest a better workaround so that no "use" tax is applied to a voucher. The current setup does the below -

a) Suppose, the sales tax % is 10. When the merchandise amount on the voucher being $100, $10 is applied as sales tax. In this case, no use tax is calculated. No action required.

b) Suppose, the sales tax % is 10. When the merchandise amount on the voucher being $100, $7 is applied as sales tax. In this case as well, no use tax is calculated (since we have setup at Payables Options > Tax Option Tab > Difference Option as NA). No action required.

c)