public function roundUnit($unit, $precision = 1, $function = 'round')
    {
        $metaUnits = [
            // @call roundUnit
            'millennium' => [static::YEARS_PER_MILLENNIUM, 'year'],
            // @call roundUnit
            'century' => [static::YEARS_PER_CENTURY, 'year'],
            // @call roundUnit
            'decade' => [static::YEARS_PER_DECADE, 'year'],
            // @call roundUnit
            'quarter' => [static::MONTHS_PER_QUARTER, 'month'],
            // @call roundUnit
            'millisecond' => [1000, 'microsecond'],
        ];
        $normalizedUnit = static::singularUnit($unit);
        $ranges = array_merge(static::getRangesByUnit(), [
            // @call roundUnit
            'microsecond' => [0, 999999],
        ]);
        $factor = 1;
        if (isset($metaUnits[$normalizedUnit])) {
            [$factor, $normalizedUnit] = $metaUnits[$normalizedUnit];
        }
        $precision *= $factor;

        if (!isset($ranges[$normalizedUnit])) {
            throw new InvalidArgumentException("Unknown unit '$unit' to floor");
        }

        $found = false;
        $fraction = 0;
        $arguments = null;
        $factor = $this->year < 0 ? -1 : 1;
        $changes = [];

        foreach ($ranges as $unit => [$minimum, $maximum]) {
            if ($normalizedUnit === $unit) {
                $arguments = [$this->$unit, $minimum];
                $fraction = $precision - floor($precision);
                $found = true;

                continue;
            }

            if ($found) {
                $delta = $maximum + 1 - $minimum;
                $factor /= $delta;
                $fraction *= $delta;
                $arguments[0] += $this->$unit * $factor;
                $changes[$unit] = round($minimum + ($fraction ? $fraction * call_user_func($function, ($this->$unit - $minimum) / $fraction) : 0));
                // Cannot use modulo as it lose double precision
                while ($changes[$unit] >= $delta) {
                    $changes[$unit] -= $delta;
                }
                $fraction -= floor($fraction);
            }
        }

        [$value, $minimum] = $arguments;
        /** @var CarbonInterface $result */
        $result = $this->$normalizedUnit(floor(call_user_func($function, ($value - $minimum) / $precision) * $precision + $minimum));
        foreach ($changes as $unit => $value) {
            $result = $result->$unit($value);
        }

        return $result;
    }