Learn Spanish (Spain): El hotel no tiene cien camas. - The hotel does not have one hundred beds.

Unlike some other numbers in Spanish, cien never changes its spelling to match the gender of the noun it describes. It is always cien, whether you are talking about cien camas (one hundred beds, feminine) or cien hoteles (one hundred hotels, masculine).

Could I use ciento here instead of cien?

No, you only use cien for exactly 100. The word ciento is used when you are adding more numbers to it, like 101 (ciento uno) or 150 (ciento cincuenta).

Why is there no word for 'does' in no tiene?

In Spanish, you don't use helper words like 'do' or 'does' to make negatives. You simply put no directly before the verb. So, no tiene translates perfectly to 'does not have'.