Using header file stdio.h you can easily do it as usual like c. before using %.2lf(set a specific number after % specifier.) using printf().
It simply printf specific digits after decimal point.
#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
double total=100;
printf("%.2lf",total);//this prints 100.00 like as C
}