How to diagnose, clear and prevent them with a Counting Frame. Make your own counting frame at a cost of £ 1.50 from an old cd case, elastic string and pony beads.
Some children's trouble with 'rounding' might stem from trying to count jumps on a number track or a 100 square:
On a number line, the middle between 0 and 10 is exactly 5. On a number track, the five is to the left of the middle. That makes it difficult to see the reason behind rounding.