TST: Use hypothesis for test_round_sanity
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them

Found this test was flaky in https://github.com/pandas-dev/pandas/runs/4275006116?check_suite_focus=true#step:7:51

Decided to parameterize the value instead of `n` so it appears in the logs and used `hypothesis` instead of 100 random values.
