This contribution inserts a checkbox in teh checkout procedure which allows your buyer to "round up" his order to the next nearest whole dollar/pound/euro etc.
Total to pay comes to $96.32. The buyer can choose to increase this to $97.00. The shop owner would then donate the 0.68 to Charity (or whatever!)...
This contribution was sponsored by Lindsay http://forums.oscommerce.com/index.php?showuser=162280
More details can be found at http://www.clubosc.com/donate-the-change.html