How much cash should I bring for 10 days in Tanzania?

I will be visiting Tanzania in September and am trying to figure out how much cash I need. I will be pn a group tour so accommodation, transportation and most activities are already taken care of. I would need cash for food and drink, souvenirs and other miscellaneous expenses which may come up. My visa is taken care of so no need to worry about that either. Would it also help to have USD on hand in case I run low on TZS and need to get more?