This is entirely up to the employer. If you have not used up all accrued vacation time, your employer should include payment for this vacation time in your final pay. However, this depends on company policy. Some companies may only pay vacation time, if you give proper notice to leave the job.
Vacation and sick leave are usually given as part of the benefits package to employees. Payment for these benefits are not required by law and are not compulsory. You can check the details of this provision on this site: http://www.dol.gov/dol/topic/benefits-leave/index.htm