The Kiwis were already 328 ahead at lunch on the final day but opted to bat on so Ross Taylor, who was six short of his hundred, could move onto three figures.
Taylor eventually reached 150 but any temptation to open the game up was resisted, allowing Gareth Hopkins time to make a maiden 50 for his country in a teatime 317 for seven declared.
Northants were therefore set 466 from 32 overs in a contest which was called off with the hosts 85 for two thanks to a fluent half-century from captain Stephen Peters.
Brendon McCullum, standing in for Daniel Vettori as captain, said: "There was obviously a temptation to declare then when Taylor reached his hundred. But at the same time, I thought it was the right decision to carry on.
"It was one of those situations where we wanted to put the hammer down in terms of our own self-belief, to build some confidence within the unit.
"That's exactly what we did. The partnership between Gareth and Ross was a positive step forward."