Well, it's actually a form of filtering but it will have the result of "softening" your shadows by giving them a penumbra. Filtering is definitely a good way to reduce aliasing (the jagged, stair-step artifacts that you're talking about), but it will also reduce the sharp details. If you want really sharp details without aliasing, then the only good solution is to increase the effective resolution of your shadow map (either by increasing the size of the shadow map, or reducing the amount of screen space that it covers). High shadow map resolution + filtering will give you sharp, unaliased shadows.