What about doing them as a Fee instead of as a Contribution. That is the way that we do it here. We did it as a Fee to simplify it for our cashiers.
You can tell it what GL you want the money to go into. Your Development would just have to pull a different report. We have a Fee Category called "Donation at Gate" that is assigned to all those Fees.
In our QuickSale setup, it is similar to Kaley's example.
With the donating cents, you could have the equivalent to a penny, nickel, dime, quarter, or half-dollar.
Just another way to think about your options,
Neil