Rounding Numbers with bc in Bash

Question

I want to compute an average with 3 decimal figures, rounded to nearest, using bc.

For example:

average of 3, 3 and 5 should yiel

Answer 1

Next function round argument 'x' to 'd' digits:

define r(x, d) {
    auto r, s

    if(0 > x) {
        return -r(-x, d)
    }
    r = x + 0.5*10^-d
    s = scale
    scale = d
    r = r*10/10
    scale = s  
    return r
}