TST: Add failing tests for minute rounding
For some minute frequencies, `.ceil()` will round up even if it should not.

- [ ] closes #21262
- [x] tests added
- [ ] tests passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @Safrone! Thanks for submitting the PR.

 - In the file [`pandas/tests/scalar/timestamp/test_unary_ops.py`](https://github.com/pandas-dev/pandas/blob/21c2b6f3cee411c26619812cd645cb40373c749c/pandas/tests/scalar/timestamp/test_unary_ops.py), following are the PEP8 issues :

> [Line 132:1](https://github.com/pandas-dev/pandas/blob/21c2b6f3cee411c26619812cd645cb40373c749c/pandas/tests/scalar/timestamp/test_unary_ops.py#L132): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace

 @Safrone happy to have a fix for this. @Safrone think ive got a potential fix for this will submit a first draft tomorrow @alimcmaster1 Awesome! closing as #21507 looks to potentially address.