Why does the time process to complete the program differ between usleep and sleep in c?

Question

#include<stdio.h>
 
main()
{
   printf("Sleep for 5 milisecond to exit.\n");
   sleep(0.005);
   printf("usleep for 5 milisecond to exit.\n");
   usleep(5000);
   return 0;
}

the sleep function takes more time to execute comparatively to the usleep function which takes seconds?