You've worked hard to get this opportunity and you want to make sure you get the most out of it. During the remaining weeks of your internship, think of this opportunity as a chance to "try on" a new role, or possibly several new roles if you're given the chance to rotate through different areas of the organization.
Handling money in the summer is like putting a load of socks through the laundry. Somehow, you lose one, never to be seen or worn again. It isn't a big deal for the most part because it's just one sock. But then you lose another couple, and one day your feet are freezing and you are left to do without.