Depending on the size of the bleeding, yes and no. The tea bag may cause the bloodcells to stick together better and in doing so form a "crust" and slowing or stopping the bleeding. You are helping the bloodcells in doing their work. Dont forget that infection is a risk with this tea bag bandage. And when you remove the tea bag you may damage the "crust" and start the bleeding all over again. So yes it can help, but no it doesnt really do any good.
This happened to me; my dentist's office told me to do this & it worked! The bleeding wouldn't stop but after biting down on the tea bag, it finally did!