Not really, it knows where it is because it has an accelerometer

Not really. It knows where it is from the GPS when it is launched and in flight, all the way until it gets jammed. Then it will revert to internal accelerometers that measure from the last confirmed GPS point. Drones do the same thing too. Jam GPS all you want, most modern military gear has the internal accelerometer backup systems. Then there is also the issue of ‘what’ GPS you are blocking. There are several different types and they each run on a different frequency, plus there is the US DOD GPS system that runs on its own system of satellites as well. And if those are US provided rounds, then you are going to have a hard time jamming them.