floating point - Does setprecision in c++ round? If so why am I seeing this?

Question

The following snippet outputs 0.29847 when I would have expected 0.29848:

double f = 0.298475;
cout << setprecision(5) << f << endl;

For other examples, however, I observe rounding:

double f = 0.123459;
cout << setprecision(5) << f << endl;

outputs: 0.12346

and

double f = 0.123454;
cout << setprecision(5) << f << endl;

outputs: 0.12345

Answer 1

The number 0.298475 isn't representable exactly in a double (since it's not a fraction whose denominator is a power of two, being 11939/40000), and the actual number that is stored is actually closer to 0.29847 than to 0.29848.