扩大100倍，否则会由于double类型的精度略微丢失，float*float =double。

#include <iostream>
using namespace std;
int main()
{
    double x;
    int a;
    double arrN[] = { 10000,5000,2000,1000,500,200 };
    double arrM[] = { 100,50,25,10,5,1 };
    cin >> x;
    x = x*100;
    cout << "NOTAS:" << endl;
    for (int i = 0; i < 6; ++i)
    {
        a = x / arrN[i];
        printf("%d nota(s) de R$ %.2f\n", a, arrN[i]/100);
        x = x - a * arrN[i];
    }
    cout << "MOEDAS:" << endl;
    for (int i = 0; i < 6; ++i)
    {
        a = x / arrM[i];
        printf("%d moeda(s) de R$ %.2f\n", a, arrM[i]/100);
        x = x - a * arrM[i];
    }


}