The chart does need improved. But what is actually happening is that the numbers are being rounded to different precisions for the dot placement and the cursor over display. If you bid .064 and .0641 they will show up in the same place and the same price displayed in cursor over box. If you bid .064 and .0643 they will now be in slightly different places, but the box will still show .064.

It wouldn't really matter at all if you could get an exact list of offers. The chart gives a pretty good impression, the list would give you actual exact offers.

You can always get the full precision of the lowest ask and highest bid in the trade tab.