If it is high side round numbers - maybe it is to shake out...

If it is high side round numbers - maybe it is to shake out short positions at stop loss/loss limit levels, low side round numbers to shake out long position stop losses. If more attention is on short position stop loss levels - then maybe big players are planning to make money when the market is going down (and want to hold more short positions via collecting at highly liquid times) and vice versa.

Maybe it is nonsense, or maybe not. Never any guarantees in trading the big stocks.