I have both E-Trade and Interactive Brokers. E-Trade allows Market sell orders on trips but only limit buys. A Market sell order could potentially go through at 5 decimals if the MMs decide to make the trade.
With IB I can input a 5 decimal point limit trade with either a buy or a sell but ultimately it is up to the MMs to decide upon the trade price. It is the 5th and 6th decimal places where they really make their money.
The statement "prolly a rookie market sell" could be true for any broker. If the MMs want to steal the shares at quad 5s, then that is what the market price is at that point in time. It was probably someone who is tired of having their money tied up in this ticker for so long.
I don't blame them. There are far too many plays occuring every day to have too much tied up. This is my lotto play. I throw little chunks of profit at $HCTI every once in a while for fun. But there are far better plays every day. GLTYA. Stay green!