function isNonPositiveInteger( x ) {
	var diff;
	var ix;

	ix = round( x );
	diff = abs( x - ix );
	return ( ( ix <= 0.0 ) && ( diff < EPS ) );
}
Tests if a finite double-precision floating-point number is a "close enough" nonpositive integer.

@private
@param {number} x - input value
@returns {boolean} boolean indicating whether the value is a "close enough" nonpositive integer