round method will round a number up if the first digit after its decimal place is 5 or higher and round down if that digit is 4 or lower. This takes in an optional argument for the precision you're looking for.
4.89.round # => 5 4.25.round # => 4 3.141526.round(1) # => 3.1 3.141526.round(2) # => 3.14 3.141526.round(4) # => 3.1415
Floating point numbers can also be rounded down to the highest integer lower than the number with the
4.9999999999999.floor # => 4
They can also be rounded up to the lowest integer higher than the number using the
4.0000000000001.ceil # => 5