// this is a version of the solution if Round is written
// as a free, non-member function

void Round(BigInt & A, int N)
// postcondition: A has been rounded to the Nth power of 10
{
    apstring s = A.ToString();
    
    if (s[N-1] >= '5')        // if digit char > '5' then round
    {
	AddPowerOfTen(A, N);
    }

    A.ZeroRight(N);
}