But 5.644 is not a round number and had a 1500 BTC ask... (that got cancelled, and not actually bought out... and this triggered a jump to 6.4)
Sometimes I use random numbers. If everyone wants to pile in at $5.80 then my trades might not be executed. But if I use $5.78921 then I will be ahead of the pack. Someone else might then say 'aha! I'm smarter, I'll grab $5.77999', and so on.
Sometimes I use funny pricing just for the hell of it.
Or it's the Manipulator playing with your mind