I am using Zen-Cart 1.35. (a bigginer)

I set every product's price is shown with taxs, but system adds another 13%.

Example
1. Cosmetics $15.00
Sales TAX 13%
must show $16.95

but it shows $19.15

Bottled Water $3.00
Sales Tax 0%
must show $3.00
but it shows $3.39

I can't find any missetting. Please give some advice.