By picking the shape and trajectory, we can have quite good accuracy on where to land the debris. Pick a piece of federal desert land and there you go.
Seriously, the scenario as I understand it is: we'd park an asteroid in a high orbit
Bad assumption right from the beginning. That's a terrible waste of energy. You mine an earth-crossing asteroid. Chunks mined off an earth-crossing asteroid can be put onto an earth-intersecting trajectory with only the tiniest of delta-V (you might have to wait a long time your payloads, but no problem there). The amount of delta-V is so low (dozens to hundreds of m/s) that you wouldn't even need to use a rocket, you could just kick it off with a railgun or similar. Then you don't brake it when it gets to earth - it brakes itself by crossing through Earth's atmosphere ("aerocapture"). There are various optional things one could do with the reentry chunks to assist, such as small rockets for trajectory adjustment en-route or small high-speed chutes to keep the asteroids from completely obliterating themselves on reentry / landing (no need for a soft landing, it's fine for them to hit moving at hundreds of meters per second). Both of these would be dwarfed orders of magnitude over by the mass of the return chunk.
All you, as a mining operation, need to do is get your operation up to the asteroid. You need to be able to mine off chunks, shaped appropriately for optimal reentry, and kick them off onto an ideal reentry trajectory toward your target impact zone - potentially with the various hardware systems described as above, but in the base case, not with anything at all. You need a source of power (solar, nuclear) for mining and to kick your chunks into their Earth-intercept trajectory. And of course you have to deal with a million and one details, starting with how to mine at all in microgravity and what targets would actually have commercially viable quantities of valuable minerals.