I found the code, but unfortunately didn't jot down the url where I found the answer.  Anyway, just for the curious, here's the C code:

<pre style="border-right:#000000 1px solid;padding-right:2mm;border-top:#000000 1px solid;padding-left:2mm;padding-bottom:2mm;margin:2mm;border-left:#000000 1px solid;padding-top:2mm;border-bottom:#000000 1px solid;background-color:#aefe50;">

Real sign(Real n)
{
        if( n > 0.0 )
                return 1.0;
        if( n < 0.0 )
                return -1.0;
        return 0.0;
}

Real TrimDecimal(Real num, Real digits)
{ 

        Real n; 

        n = num * Pow(10.0, digits); 

        n = sign(n) * Abs(Floor(n + 0.5)); 

        return n / Pow(10.0, digits); 
}

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