Truncate a float number with a desired decimal limit

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I would like to truncate a float number 1234. 056789 back to float number but with a desired fraction as the following:

1.  numb = truncate(1234. 056789, 3)  ---> numb = 1234.056

2.  numb = truncate(1234. 056789, 5)  ---> numb = 1234.05678

I did try:

float math_truncate(float numb, int n_trunc)
{
      int   i, n = pow(10,n_trunc);
      double num;
 
      i = (int)(numb * n); 
  
      num = i/(n * 1.0); 

     return (float)num;
}

Before return I have:

Case #1: num = 1234.056000000 ... after return, I have 1234.056107

Case #2: num = 1234.056780000 ... after return, I have 1234.05678107

Note1: I did try other methods, but the results are not as #1 & #2 ... always get some after the desired decimal point

Note2: The TruncateRealNumber (number) only truncate all fraction part ... num = 1234.00000)

*) Anyone can help?

[Patrick_P.]

This is a duplicate post.  See this thread.