Shipping module not working

[Speedbern]

In shipping module, we would set for example:

 

0.00kg - 0.50kg cost $1

0.51kg - 1.00kg cost $2

1.01kg - 1.50kg cost $3

1.51kg - 2.00kg cost $4 and etc etc

 

If my total weight is exactly 0.5kg or 1kg or 1.5kg or 2.00kg, it simply give a flat rate of say $10, but it is falls between 0.53kg or 1.12kg, then it follows the schedule above. I find this weird. How do I overcome this problem? Please help.