Molecular dynamics (MD) simulation is used to assess the hyper-Rayleigh scattering (HRS) depolarization ratio of liquid nitrobenzene subject to vertically polarized light. In contrast to previous theoretical work, we have quantified both incoherent and coherent scattering arising from positional and orientational inhomogeneities in the molecular distribution. Although coherent scattering is shown to be much less important than in the case of Rayleigh scattering, it can not be neglected. Therefore, our analysis supports the current practice of working with dilute solutions (for which coherent contributions to HRS are truly negligible) to extract the first molecular hyperpolarizability from HRS measurements. In cases where experiments with pure liquids can not be circumvented, our analysis may be used to separate coherent and incoherent signals. Our work, which uses as input static "gas-phase" (hyper)polarizabilities obtained from ab initio calculations, also provides information on the orientations and magnitudes of the local electric fields experienced by the individual molecules in the liquid. For nitrobenzene it is found that the local fields are largely determined by specific dipolar alignment between neighboring pairs of molecules, with consequences on the HRS signal.