Umm, Astro, I think the people in Nagasaki circa 1945 would disagree about the effects of ionizing rads further out than 5 miles on bombs under 1kt.
I never said anything regarding fallout, which is a large problem just five miles from a nuclear detonation, especially a groundburst. In terms of the initial blast, though? An utter non-factor at that distance; in fact, the smaller the nuke is, the relatively more dangerous the ionizing radiation gets. Read this
FAQ; I've already linked to the relevant page in it.
And Mars, no I do not mean tactical; a modern strategic warhead is indeed usually 3-500 kT. It's more efficient to use a whole bunch of smaller devices on a dispersed target like a city in a circular pattern than detonating one really big one over the target's center. Doing so increases the area over which a large amount of blast overpressure (greater than ~10 psi) is generated, thus destroying more hard targets. On a side note, it is a cruel irony that going with a counterforce strategy (targeting factories, military bases, railyards, etc.) over a countervalue one (targeting population) kills more people. This is because of the heavily increased fallout from all the groundbursts needed to get the required overpressure to destroy all the targets. A countervalue strategy is more effectively carried out using airbursts, so you can maximize the area over which the thermal pulse starts fires and inflicts lethal 3rd-degree burns. Fun fun.