BUG: Fix dt64[non_nano] + offset rounding

Author: Aniketsy

pandas/core/arrays/datetimes.py

@@ -45,7 +45,6 @@
     tzconversion,
 )
 from pandas._libs.tslibs.dtypes import abbrev_to_npy_unit
-from pandas._libs.tslibs.timedeltas import Timedelta
 from pandas.errors import PerformanceWarning
 from pandas.util._exceptions import find_stack_level
 from pandas.util._validators import validate_inclusive
@@ -82,6 +81,7 @@
         Iterator,
     )
 
+    from pandas._libs.tslibs.timedeltas import Timedelta
     from pandas._typing import (
         ArrayLike,
         DateTimeErrorChoices,
@@ -824,13 +824,8 @@ def _add_offset(self, offset: BaseOffset) -> Self:
                 "s",
             ]
             res_unit = self.unit
-            offset_td = getattr(offset, "offset", None)
-            if (
-                offset_td is not None
-                and isinstance(offset_td, Timedelta)
-                and offset_td.value != 0
-            ):
-                ns = abs(int(offset_td.value))
+            if isinstance(offset, Tick):
+                ns = abs(int(offset.value))
                 if ns == 0:
                     eff_unit = self.unit
                 elif ns % 1_000_000_000 == 0: