Bug with sale items and 100% discount coupon

When an items price ends in an odd cent and is on sale (50% off was what I was using) and then the item is paid for using a coupon discounting it for 100% (free) the item will show up with 1 cent still due...

Example:

All items from Manufacturer X are on 'sale' at 50% off and a member has a coupon for a free item (100% discount). They choose Item B, which is normally 3.99, but the sale price (50% off) shows as $2.00... they use their coupon code for the 100% discount and it shows a total due of $0.01. Apparently it has something to do with the extra fractions of a cent, it only happens on products with a price ending in an odd number.

If you bump the normal price up to $4.00 even it doesn't happen. :)

I was able to recreate this several times.

In reference to this thread: http://www.zen-cart.com/forum/showthread.php?t=50051