1, 0.5 + 0.5 + 0.5 - 0.5
2, 0.5 + 0.5 + 0.5 + 0.5
3, ( 0.5 + 0.5 + 0.5 ) / 0.5
4, 0.5 / 0.5 / 0.5 / 0.5
5, 5 * 5 / sqrt(5) / sqrt(5)
6, 55 / 5 - 5
7, 5 + ( 5 + 5 ) / 5
8, ( 0.5 * 5 ) + 5 + 0.5
9, 5 + 5 - ( 5 / 5 )
10, ( 55 - 5 ) / 5
11, 5 + 5 + ( 5 / 5 )
12, ( 55 + 5 ) / 5
13, ( 5! - 55 ) / 5
14, 5! / 5 - 5 / 0.5
15, ( 5 + 5 ) / 0.5 - 5
16, 55 / 5 + 5
17, 5! / ( 5 + 5 ) + 5
18, ( 5! - 5 ) / 5 - 5
19, ( 5! - 5 * 5 ) / 5
20, 5 / 0.5 + 5 / 0.5
This took me around 35 to 45 minutes of testing different combinations in a calculator, I hope that this satisfies what you needed.
Please note that most people probably wouldn't have be willing to spend this much time, but I was happy to help you on the Four Fives puzzle.