BUG: timedelta.round fails to round to nearest day about pandas

[bergnerjonas]

Tried to reproduce. Your example for .round on a Series fails for me as well, however rounding single timedeltas (e.g. pd.Timedelta('1 days 23:18:00').round('d')) works fine.

[rhshadrach]

Thanks for the report! Result of a git bisect:

commit 6dbeeb4009bbfac5ea1ae2111346f5e9f05b81f4
Author: Lumberbot (aka Jack)
Date:   Mon Jan 8 23:24:22 2024 +0100

    Backport PR #56767 on branch 2.2.x (BUG: Series.round raising for nullable bool dtype) (#56782)
    
    Backport PR #56767: BUG: Series.round raising for nullable bool dtype
    
    Co-authored-by: Patrick Hoefler

cc @phofl

Note that ser.dt.round('d') still works. I don't believe that Series.round having special logic for different dtypes is documented anywhere.

[phofl]

Yeah this is a bit weird, DataFrame.round never worked for those, Series.round now follows this behavior. We can either make both work or keep as is

[rhshadrach]

Making this work for DataFrame.round seems undesirable - numeric columns would take the number of digits as an argument whereas timedelta/datetime would take a frequency. I'd lean toward keeping this as-is.