Free quantity rounding off

Hai,

In Order Management Module we are using automatic modifier to generate the free quantity against the sales order quantity.
 
Case explained below with example
 
Item - A0025
 
Sales Quantity : 0 to 16 – No Free Quantity
Sales Quantity from 17 onwards – 3 Quantity free on incremental basis, i.e. for every 5.66 quantity (17/3) 1 quantity free.
If the customer ordered for 56 quantity,  system will automatically provide the free quantity of 9 i.e. 56/5.66 = 9.894
Our requirement is if the calculated value is below 9.5; the quantity needs to be rounded to 9 and if the calculated
value is equal to or above 9.5 the quantity needs to be rounded to 10.
 
Existing System