Any slope stability program can be used to analize a reinforced slope. The reinforced area can be set up as a different soil type with a high cohesion. This will force the failure surface outside of the reinforced area.
Note that the reinforced area for the stability model does not extend to the back end of the geogrids. You have to make a proffesional judgement as to how far from the end of the grids you have to be to have a significant impact on the strength of the soil.
In my experience, this method works much better than the geogrid reinforcing lines that some software allows you to add to the stability model.