SimpleUnitConverter has a small accuracy issue

Sometimes, when converting floating-point numbers, SimpleUnitConverter will change the number to be converted and/or the answer.

Steps to reproduce:
1. Download SimpleUnitConverter version 0.4 (using this version makes the issue more obvious)
2. Launch SimpleUnitConverter
3. Enter option 1
4. For "Enter degrees Celsius", enter 22.1
5. The result is "22.10000 degrees equals 71.780001 degrees Fahrenheit".

The actual result of the formula should be 71.78 degrees Fahrenheit (calculated with a calculator).

Another (slightly more glaring) example:
Do steps 1-2 above
3. Enter option 2
4. For "Enter degrees Fahrenheit", enter 39.22
5. The result is "39.20001 degrees Fahrenheit equals 4.011112 degrees Celsius".

The actual result should be 4.011111111 degrees Fahrenheit.

I know, it's a minuscule error, but it still needs to be fixed.

What to do about it:

I have no idea. I am looking for a more experienced developer to kindly help me figure out why this behavior is happening and how to fix. (I am a newbie developer, ~2-3 months)