BUG: rounding datetime in series is broken

[Andre-Medina]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

pd.Series([pd.to_datetime("2022-01-09T12:00:01")]).round("30min") == pd.Series([pd.to_datetime("2022-01-09T12:00:01").round("30min")])

Issue Description

Repeat of issue of #57002

Expected Behavior

example should return true

Installed Versions

INSTALLED VERSIONS

commit : d9cdd2e
python : 3.10.13.final.0
python-bits : 64
OS : Linux
OS-release : 5.15.153.1-microsoft-standard-WSL2
Version : #1 SMP Fri Mar 29 23:14:13 UTC 2024
machine : x86_64
processor :
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.2.2
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.9.0
setuptools : 69.1.0
pip : 24.0
Cython : None
pytest : 8.1.1
hypothesis : None
sphinx : None
blosc : None
feather : None

[MarcoGorelli]

dupe of #57002, please don't repost