function round(num, digits)
	-- banker's rounding
	local mantissa = 10^digits
	local norm = num*mantissa
	norm = norm + 0.5
	local norm_f = math_floor(norm)
	if norm == norm_f and (norm_f % 2) ~= 0 then
		return (norm_f-1)/mantissa
	end
	return norm_f/mantissa
end