When spherical tensors are rotated by certain angles, coherence transfer selection rules may apply. For example, a pi rotation cleanly inverts the coherence order. A pi/2 rotation of a T-0(1) tensor creates only T-+/- 1(1) tensors. In this work estimations are given for the coherence transfer leakage under the action of rotations with small errors in the rotation angle or axis. Although the theory is stated with particular applications to NMR (nuclear magnetic resonance) in mind it is equally applicable wherever nonideal rotations of spherical tensors are considered (e.g., quantum computing and relaxation theory). In NMR it is useful for the estimation of coherence transfer leakage, especially in pulse sequences with many n pi pulses. The results are also applicable to spinors and half-integer representations of the rotation group.