We investigate numerically dipole solitons in highly nonlocal three-dimensional uniaxial nematic liquid crystals in the presence of an externally applied bias voltage. Using the modified Petviashvili method, we calculate shape-invariant dipole profiles. We study the influence of boundary conditions and finite size effects on the dipole solitons obtained. We show that the solitons found in one transverse dimension may differ dramatically from solitons of the same family, but found in two transverse dimensions. We report the existence of crystal thicknesses for which a specific dipole soliton from a given family of dipole solitons achieves minimal power and maximal width.