How to stop tiny physics objects from falling through the floor?

Well, everything in my game is set to real-world scale, so I figured the money should be too.
I actually wouldn’t mind too much scaling them up a tad, but they still fall through landscapes even when at <15x the scale.

I plan on having events and enemy interactions around these coins, the player can even throw them. I was planning on having them be pretty involved in the gameplay and the game itself.

I’m quite open to discussing ideas if you have any tho.