This is an irregular verb. It follows the conjugation pattern of the verb pensar.
PresentPresente
Las tiendas cierran a las nueve los domingos.
The stores close at nine on Sundays.
PreteritePretérito indefinido
Anoche cerré la ventana porque hacía frío.
Last night I closed the window because it was cold.
ImperativeImperativo afirmativo
Antes de salir, cierra todas las ventanas.
Before leaving, close all the windows.