Honahble Sahn say ...
"Floating point number like pile of sand on the ground. Each time you pick one up and move it, you lose a little sand and pick up a little dirt."
You are always going to find a certain amount of imprecision in any floating point calculation. (Even those performed by your trusty pocket calculator.)
This includes: imprecision during the calculation; truncation that can occur when storing the value in memory areas of various sizes; errors that occur in translating your character input into binary; and errors which occur in translating the binary data to decimal characters for your viewing pleasure!
It's normal. Every computer application, not just MySQL, exhibits this behavior.