C++的基本现金系统

在下面的代码中，我有一些错误，我不知道为什么它不起作用。

我用fmod做小数，但我在给你 0.10 和 0.05 $ 的部分遇到了一些错误，而且大多数时候我从来没有得到我应该回馈的好金额如果有的话。

#include<iostream>
#include <cmath>
using namespace std;
int main() 
{
int iAmount_due = { 0 };
int iGiven_money = { 0 };
int iMoney_back;
iMoney_back = iGiven_money - iAmount_due;

cout << "Enter the amount due please: " << endl;
cin >> iAmount_due;
cout << "Enter the amount given please: " << endl;
cin >> iGiven_money;

if (iGiven_money >= iAmount_due) {
iMoney_back = iGiven_money - iAmount_due;
cout << "We will give you : " << iMoney_back << " $ back" << endl;
}
else {
cout << "No money back" << endl;
}

if (iMoney_back >= 100) {
cout << "You will receive: " << iMoney_back % 100 << " x 100$" << endl;
}
else {
cout << "No 100$ bill" << endl;
}

if (iMoney_back >= 50) {
cout << "You will receive: " << iMoney_back % 50 << " x 50$" << endl;
}
else {
cout << "No 50$ bill" << endl;
}

if (iMoney_back >= 20) {
cout << "You will receive: " << iMoney_back % 20 << " x 20$" << endl;
}
else {
cout << "No 20$ bill" << endl;
}

if (iMoney_back >= 10) {
cout << "You will receive: " << iMoney_back % 10 << " x 10$" << endl;
}
else {
cout << "No 10$ bill" << endl;
}

if (iMoney_back >= 5) {
cout << "You will receive: " << iMoney_back %  5  << " x 5$" << endl;
}
else {
cout << "No 5$ bill" << endl;
}

if (iMoney_back >= 0.25) {
cout << "You will receive: " << fmod (iMoney_back, 0.25) << " x 0.25$ " << endl;
}
else {
cout << "No 0.25$ " << endl;
}

if (iMoney_back >= 0.10) {
cout << "You will receive: " << fmod (iMoney_back, 0.10) << " x 0.10$ " << endl;
}
else {
cout << "No 0.10$ " << endl;
}

if (iMoney_back >= 0.05) {
cout << "You will receive: " << fmod (iMoney_back, 0.05) << " x 0.05$ " << endl;
}

else {
cout << "No 0.05$ " << endl;
}

return 0;
}