BUG: Fix dt64[non_nano] + offset rounding

Author: Aniketsy

pandas/core/arrays/datetimes.py

@@ -46,6 +46,7 @@
     tzconversion,
 )
 from pandas._libs.tslibs.dtypes import abbrev_to_npy_unit
+from pandas._libs.tslibs.offsets import DateOffset
 from pandas.errors import PerformanceWarning
 from pandas.util._exceptions import find_stack_level
 from pandas.util._validators import validate_inclusive
@@ -71,8 +72,6 @@
 
 from pandas.tseries.frequencies import get_period_alias
 from pandas.tseries.offsets import (
-    BusinessHour,
-    CustomBusinessDay,
     Day,
     Tick,
 )
@@ -827,7 +826,7 @@ def _add_offset(self, offset: BaseOffset) -> Self:
             ]
             res_unit = self.unit
             if hasattr(offset, "offset") and offset.offset is not None:
-                if isinstance(offset, (CustomBusinessDay, BusinessHour)):
+                if not isinstance(offset, DateOffset):
                     offset_td = Timedelta(offset.offset)
                     if offset_td.value != 0:
                         offset_unit = offset_td.unit