Rounding off in peculiar cases

I have to do some work calculations. The increment of an employee is 3p.c. of Band Pay Plus Grade Pay. If the integral part of the result is a multiple of ten and the fractional part is less than .50, then the increment gets rounded to the integral part alone. But if the Integral part is any other than a multiple of 10 then the increment gets rounded off to the next higher 10 rupees. How can I write a formula for this?