UUsing scanning tunneling microscopy and a careful selection of chiral molecules and anchoring groups, we systematically investigated magnetoresistance associated with the chirality-induced spin selectivity (CISS) effect. We observed a reversal of the magnetoresistance signal upon reversing the magnetization direction, molecular chirality, or molecular orientation. These observations can be rationalized by associating an axial vector with the chiral molecule and considering its orientation relative to the substrate magnetization. Within this framework, the polar electric dipole moment of the molecule does not directly determine the magnetoresistance response, whereas an axial vector associated with the molecular magnetic polarization provides a more natural description. Such an axial vector may play an important role in the emergence of an interfacial magnetic moment at the junction between the molecule and the metallic electrode.