Shinobi Tactics is the third upgrade of Path 2 for the Ninja Monkey in BTD6. It allows all Ninjas around its radius to increase attack speed by 8% (multiplicative). This upgrade can stack up to 20 times. It costs $765 on Easy, $900 on Medium, $970 on Hard and $1,080 on Impoppable.
Usually, it is best to leave Shinobi Tactics as 0-3-0, unless it is to increase Shinobi Tactics coverage range, in which 1-3-0 should be enough range to reach nearby high-level Ninjas for that significant attack speed boost.
If there are multiple Shinobi Tactics around a Bloonjitsu or Grandmaster Ninja, those high-level ninjas will not necessarily require crosspathing with Path 2, as Shinobi Tactics Ninjas already come with decently reliable Distraction and Counter-Espionage attacks, particularly when in very large groups.