How much is a lot? If asking about bills, I'd presume over ¥2000. If that is indeed the case, how could you let that situation get so out of control? Especially if it is only change of the small variety.

I'd suspect that it is not that much and the other advice about using the 10's and 5's for train fare or for cheap consumer goods would be about the best you're going to get without looking silly if you don't wish to go the charity route (my preferred choice as well).