Returns a number rounded to the nearest integer value or to a specified number of decimal places. Numbers halfway between two rounding values are rounded up. For example 23.5 rounds up to 24.
Parameter 1 - a numerical value (a).
Parameter 2 (Optional) - number of decimal places to round to (b). If omitted, rounding is to the nearest integer.
Returns: a number equal to floor(a+0.5) or (floor(a*10^b + 0.5))/10^b.