I notice that even past 4 decimals, I instantly noticed a difference. For instance, my current sens is 2.17725, and I instantly notice a difference between 2.1772 and 2.17725. The thing is, I believe that the amount of numbers you can have is actually unlimited, but to an extent, you don't notice a huge difference.
I believe you should take off the limitation of decimals to allow any sens to travel over to all games if possible.