I thought US Dollars wouldn't fit either until I changed the way I was rolling them. You can fit 1 bill in the small bison by doing this:
1. Hold the bill so you can read it
2. fold it in half, right to left
3. fold that half of the dollar into thirds... right to left (so you have 3 flaps that fold up)
4. Now you have a sliver of a bill that you can still somewhat read... and the width is a bit smaller than the length of the bison capsule... now roll it up or down.. your preference...you'll have to do this pretty tightly. sometimes it takes me twice to do it
5. Amazingly, this is now just smaller than the bison capsule. Place it in the capsule going in the same direction as the capsule closes (it's easier as it doesn't catch the lid as you close it)...

Now you can have money in a small Bison capsule and nobody ever guesses you have an emergency $50 always with you... It's saved me several times in shopping emergencies... and I always immediately refill it! Have fun!