Eventually, Nike missiles had a selectable yield nuclear warhead. The first salvo was set to intercept at 90 miles away, with 40 Kiloton of yield. The next was 45 miles away, and 20 Kiloton, and the "Hail Mary" was directly overhead, with 2 Kiloton yield.
They initially had conventional warheads as I recall and they were primarily intended as bomber defense. They'd explode a warhead above a flight of bombers so they'd be hit by a massive shock wave.