diff --git a/masque/utils/transform.py b/masque/utils/transform.py
index ccdf3d2..fb84052 100644
--- a/masque/utils/transform.py
+++ b/masque/utils/transform.py
@@ -6,6 +6,7 @@ from functools import lru_cache
 
 import numpy
 from numpy.typing import NDArray
+from numpy import pi
 
 
 @lru_cache
@@ -21,6 +22,11 @@ def rotation_matrix_2d(theta: float) -> NDArray[numpy.float64]:
     """
     arr = numpy.array([[numpy.cos(theta), -numpy.sin(theta)],
                        [numpy.sin(theta), +numpy.cos(theta)]])
+
+    % If this was a manhattan rotation, round to remove some inacuraccies in sin & cos
+    if numpy.isclose(theta % (pi / 2), 0):
+        arr = numpy.round(arr)
+
     arr.flags.writeable = False
     return arr