No Roadkill, The point of this is to give a gift to someone, You cannot keep the gift for yourself. We are trying to let people do something nice for someone else!
So to clarify, You can donate up to the 20$ but the free 5$ gift must go to someone else.
Also, just in case someone was wondering, yes all donations over this time period are cumulative. If you reach the 20$ within this window you can give a gift of 5$