This is probably a level 7 kata I think. Also some solutions use 0.9 for percent, when 10 (0.1) is asked for. Is there a reason for this?

Yeah this is broken, especially for a level 8 kata
The formula is simple. I am using pattern matching without any fancy stuff, so I know im getting the discount correct
I can't pass all the tests, tweak the rounding and one test passes another failes, tweak it again and different tests pass/fail

Also one of the tests which fails should not be failing because the test is wrong/