One has to have access to Level 3 trading
to put orders in more than 4 decimals deep.
If your 'bid sitting' and they want shares you
won't see them on Level 2 where you can only
put a trade in max of 4 decimals such as .0412....so
if the one using level 3 wants shares they
put their bid in anywhere above yours and
can use more than 4 decimals such as .04121.
The reverse is true if they want to sell under
the Level 2 'ask price' ....such as if your on Level 2
and are the low ask , say .0443 the one
using level 3 can put a sell in at .04429 and thats
what you get when you buy..
Bottom line is that those that have level 3 access have
the advantage over those using level 2.