How to roundoff given real number to nearest integer(Optimizing Algorithm/Program Step by Step)

Without using builtin function round,ceil,floor..

Example:
if f = 3.7 then i = 4
if f = 3.2 then i = 3

Code:

General logic:

int roundoff(float n)
{
int k = (n *10) %10;
if(k>5)
k=n+1;
else
k=n;
return k;
}

Optimized : int roundoff(float n)
{
int k = n + 0.5;
return k;
}