Zen Cart 1.2.6

On check out for instance,

($9 + $2)

+ $8.12 shipping
--------------------
$1.29 Tax


My calculator reads 20.41

But zencart adds it as $20.42 . . . . WHAT GIVES . . this is fifth invoice the accountant has sent to us with this issue and others.

The other issue I had earlier after the install was it was adding with some crazy method of product price then tax then subtracting a discount, when it should always be tax on the total price not what it was before discounts . . . who figured out the math for this thing??

Is this common? If so I need to change to a different cart. Please let me know.

Thanks.