A small bag of marijuana worth $10.00. In Toronto, the going weight for a dimebag is around one gram, but this probably varies from location to location.
The origin of the term may stem from the fact that a dime is ten cents, and a dimebag is ten dollars, reinforced by the nickelbag ($5 worth of marijuana) and the quarter (a quarter-ounce of marijuana).
"Can I get a dimebag off you?"
"Sure, but if you can you should get more, save some cash."