Tapping/clicking noise when braking.

Could be a rock in the rotor, or even a bad axle.
Take it to a mechanic who will put it on a lift and go over everything with you

 

Can't really help much, but I will say I had that exact same noise for a while and I could never figure it out. I checked the brakes multiple times (almost sure it was from the front). It went away eventually and unfortunately it wasn't really on my mind at the time, so I'm not sure when exactly. Only thing I've done to the front brakes since the noise is bleed them (the old fashioned way) and grease the slider pins, but I think the noise went away before I did both those. I would never trust a dealership, but in this case I bet they truly couldn't figure it out and probably most mechanics would say your brakes are fine so don't worry about it. If you do figure it out, let me know.

 

Is the clicking more prominent in turns at low speed?

 

What would that imply?

 

Have it for years . Annoying but I’ve had no problems.

 

Same. I’ve owned my Prius for 8 years and can’t remember when I didn’t have the low speed slowdown clicks. Doesn’t happen all the time, and also can’t hear it unless like the op said where the windows are down, gradually slowing down to something like a stop sign. There are a lot of noises on the Prius where it feels like chasing ghosts…

 

Likely thinking of CV joints.

 

CV joint(s). It's apparently not a problem, as long as they're quiet under power. My Mazda made similar clicks, even when not in a curve.

 

I see, that must be my case because it's definitely more prevalent on turns. I wonder if that's why my front end sounds like it's about to come apart when I drive on bumpy gravel roads, despite my suspension and steering feeling quite solid?