Absolutely. The $100's are for getting a hotel room or something. The $20's are likely the largest other merchants will break.

My emergency cash stash has a couple $100's and a ton of $5's because I'm not super limited on space, and when everyone else has $20's and needs them broken, a bunch of $5's makes everything easy, and beats carrying a whole bucket of $1's. Learned that at flea-markets.