A systematic study has been undertaken to determine how local distortions affect the overall (molecular) magnetic anisotropies in binuclear complexes. For this purpose we have applied a series of distortions to two binuclear Ni(II) model complexes and extracted the magnetic anisotropy parameters of multispin and giant-spin model Hamiltonians. Furthermore, local and molecular magnetic axes frames have been determined. It is shown that certain combinations of local distortions can lead to constructive interference of the local anisotropies and that the largest contribution to the anisotropic exchange does not arise from the second-rank tensor normally included in the multispin Hamiltonian, but rather from a fourth-rank tensor. From the comparison of the extracted parameters, simple rules are obtained to maximize the molecular anisotropy by controlling the local magnetic anisotropy, which opens the way to tune the anisotropy in binuclear or polynuclear complexes.