Increases attack speed and pierce of nearby Ninjas. Stacks 20 times.
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) and pierce by 8% (additive). 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.
Adding Shinobis for pierce buffs will greatly improve the shurikens of every Ninja in range; adding enough Shinobis nearby each other will allow them to produce excellent Distraction blowback to massive amounts of Ceramics, particularly on Rounds 81+.
To clarify the mechanics of pierce buffs with partial pierce (e.g. 1.5 pierce), partial pierce will be treated as "every 1/X shots, pierce increased to Y + 1", where X is the decimal part and Y is the integer part. So for example, 1.5 pierce would be treated as "every 2nd shot, pierce increased to 2" Link.
One 0-3-0 Shinobi Tactics Ninja costs $2390 on Hard Difficulty. Having 20 of them costs $47,800 on Hard Difficulty. This is especially important in CHIMPS Mode, as it is often unwise to over spend on unnecessary Shinobi Tactics Ninjas that do not improve Grandmaster Ninja or Master Bomber.
In Version 11.0, the old description was changed from "Increases attack speed of all ninjas nearby - more Shinobi means more attack speed." to the new description, due to both the need to highlight the maximum stacking limit and to accommodate the inclusion of the new pierce buff.