c++ - Source code to round floating point number

Question

Other than using any inbuilt function like ceil and floor how can you round a floating point number?

I want to convert 2.10 to 2.14-> 2.1 and 2.15 to 2.19 -> 2.2

I wrote some logic but stuck in the middle

    float a = 2.24;
    int b = a*100;
    int result n, i =0;
    while(i>2)
    {
        n = b%10;
        i++;
    }
    if(n >5)
    {
      c = b%10;
      c = c/10 + 1;
    }

I tried lot of inbuild function but all that not workign for my diab compiler

//  totalDist = roundf(totalDist * 10) / 10.0;      
//  totalDist = floor(totalDist * pow(10., 1) + .5) / pow(10., 1);  
    totalDist = floorf(totalDist * 10 + 0.5) / 10;

planning to write my own logic

Answer 1

float a = 2.24;
float b = roundf(a*10.0f)/10.0f;//roundf in C99