Comparison of chemical shifts among alkanes in NMR spectroscopy
A carbon atom is slightly more electronegative than a hydrogen atom. For tertiary hydrogens, the extra bonded carbons will inductively withdraw more electron density from the hydrogen. This means the hydrogen will be deshielded slightly more, and resonate at a higher ppm. 

I would classify cyclopropane in its own class, as its molecular orbitals make it somewhat unique. The C-C bonds do not exhibit exclusive sigma bond characteristics, and due to that phenomenon the hydrogens will hold slightly more electron density.