  We show that a shell-model version of the three-dimensional
Hall-magnetohydrodynamic (3D Hall-MHD) equations provides a natural theoretical
model for investigating the multiscaling behaviors of velocity and magnetic
structure functions. We carry out extensive numerical studies of this shell
model, obtain the scaling exponents for its structure functions, in both the
low-$k$ and high-$k$ power-law ranges of 3D Hall-MHD, and find that the
extended-self-similarity (ESS) procedure is helpful in extracting the
multiscaling nature of structure functions in the high-$k$ regime, which
otherwise appears to display simple scaling. Our results shed light on
intriguing solar-wind measurements.
