TST: numpy RuntimeWarning with Series.round()
- [x] closes #14197
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ n/a] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=h1) Report
> Merging [#25432](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/85572de5e7bb188cfecc575ee56786406e79dc79?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25432/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25432   +/-   ##
=======================================
  Coverage   91.74%   91.74%           
=======================================
  Files         173      173           
  Lines       52923    52923           
=======================================
  Hits        48554    48554           
  Misses       4369     4369
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.31% <ø> (ø)` | :arrow_up: |
| #single | `41.73% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=footer). Last update [85572de...7994f6a](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=h1) Report
> Merging [#25432](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/85572de5e7bb188cfecc575ee56786406e79dc79?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25432/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25432   +/-   ##
=======================================
  Coverage   91.74%   91.74%           
=======================================
  Files         173      173           
  Lines       52923    52923           
=======================================
  Hits        48554    48554           
  Misses       4369     4369
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.31% <ø> (ø)` | :arrow_up: |
| #single | `41.73% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=footer). Last update [85572de...cb0fde0](https://codecov.io/gh/pandas-dev/pandas/pull/25432?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @gfyoung : Missing-data? what is required? @simonjayhawkins : `missing-data` refers to issues that involve missing data / null values (you can see the same label in the issue you're closing here).  It has nothing to do with the fact that your PR is missing any information.  Your PR is just fine in that regard.  🙂  @gfyoung : thanks 😊  thanks @simonjayhawkins 