The sale may be over, I picked up a set of Hifiman Edition S which are very easy to drive without an amp, the sound quality and comfort are excellent. Even on sale they were above your budget a bit but really great performance for the price, even at full price. I believe they have less expensive as well, not sure if over the ear. What impresses me about the Edition s is how well they sound from just my iPhone.
The Grado I69 are below $99 and also easy to drive. I can't say how well they do for long term comfort.
I'm not up on all the specs but you want to look for a set that's easy to drive so you get good performance just from your tablet.
Sony and Pioneer both offer decent headphones under $99, don't know any models by heart.