Example: Go to the store and spend $32.24, BofA charges you the $32.24 and takes $0.76 from your checking account and deposits it into your savings account.Better yet, for the first three months BofA equally matches your "change", so you basically get free money. After the first three months, matching drops to 5%, but it's still better than what your bank is giving you (nothing).
Anyhoot, it's a nifty program. I'm a Keep Your Change-er. Loving it. Saving about $30 a month I otherwise wouldn't be saving (earning interest on, etc.) Maybe not a reason to switch banks, but it's close.