import math


def rounds_sig(value, sig=3):
    """Round a float to sig significant digits & return it as a string.

    Parameters
    ----------
    value: float
       The float that is to be rounded.
    sig: int
        The number of significant figures.

    Returns
    ----------
    str:
        The rounded output string.
    """
    if value == 0.:
        return str(0.)
    if value < 0.:
        value = abs(value)
        return str(-1. *
                   round(value, sig - int(math.floor(math.log10(value))) - 1))
    return str(round(value, sig - int(math.floor(math.log10(value))) - 1))