Is SbF5 symmetrical?
As mentioned in the comments, $\ce{SbF5}$ in the gas phase has a rather high symmetry, the point group looks like $D_\mathrm{3h}$ to me, containing a principal three-fold rotational symmetry axis (along the axial bonds) and three two-fold axis (along each of the equatorial bonds), among other operations. As mentioned in this text, a dipole moment can only coincide with a rotational axis. Since there are four such axis in the molecule, it cannot have a dipole moment.

Note however, that each of the bonds is certainly polar. They just cancel out, as could be proven by vectorial addition of the bond dipole moment.