Have fun while you learn mathematics with this CT-555 N Basic calculator which is exclusively designed with special features to meet the basic needs of young students and professionals. . Tax Calculation Function . Now, calculating tax values is made easy with the help of this Citizen calculator which is designed with a special tax calculation function. . Automatic Power Off . When there is no key entry for a longer time, the calculator gets switched off automatically to save the battery life. The check and correct function enables you to recall and edit the wrongly entered data. . Square Root . The Square Root function helps you to calculate the root value of a particular number that you enter.