How do I determine the value of a variable with an "if statement" (for c++)

I am writing a "vending machine" code for c++ and I need to have 5 items where 3 items cost an integer amount and the other 2 cost a decimal amount.

I am only using if statements in this code but there is an error with my "cost" variable. Can someone help me with my error?

Edit: the code works after I added float cost = 0; to my code. However, there is an error with the logic of calculating the payment. For example, when I buy a $3 item and pay with $1, I get a $1 change. Can anyone help me with that?

Thanks in advanced!

Code below:

#include <iostream>
using namespace std;

int main() {

  cout << "Vending Machine" << endl;
  cout << "----Items------" << endl;
  cout << "1. Popcorn: $2" << endl;
  cout << "2. Coconut Clusters: $3" << endl;
  cout << "3. Granola Bar: $2.50" << endl;
  cout << "4. Trail Mix: $1.50" << endl;
  cout << "5. Chocolate: $1" << endl;

  cout << "Enter you selection: " << flush;
  int input;
  cin >> input;
  float cost = 0;


  if (input == 1) {
    cout << "You added Popcorn to your cart." << endl;
    float cost = 2;
    cout << "Your total is $" << cost << endl;
  }
  
  if (input == 2) {
    cout << "You added Coconut Clusters to your cart." << endl;
    float cost = 3;
    cout << "Your total is $" << cost << endl;
  }
  
  if (input == 3) {
    cout << "You added Granola Bar to your cart." << endl;
    float cost = 2.50;
    cout << "Your total is $" << cost << endl;
  }

  if (input == 4) {
    cout << "You added Trail Mix to your cart." << endl;
    float cost = 1.50;
    cout << "Your total is $" << cost << endl;
  }

  if (input == 5) {
    cout << "You added Chocolate to your cart." << endl;
    float cost = 1;
    cout << "Your total is $" << cost << endl;
  } 

  

  cout << "Pay amount: " << flush;
  float money;
  cin >> money;

  if (money > cost) {
    float change = money-cost;
    cout << "Thank you! You have $" << change << " change." << endl;
  }

  if (money == cost) {
    cout << "Thank you! Have a nice day!." << endl;
  }

  if (money < cost) {
    float amountOwed = cost-money;
    cout << "Please insert another $" << amountOwed << endl;

    cout << "Enter amount: " << flush;
    float payment;
    cin >> payment;

    if (payment > amountOwed) {
    float change2 = payment-cost;
    cout << "Thank you! You have $" << change2 << " change." << endl;
    }

    if (payment == amountOwed) {
      cout << "Thank you! Have a nice day!." << endl;
    }

    if (payment < amountOwed) {
      cout << "Sorry, you did not enter enough money. Your cart has emptied." << endl;
    }

  }
  return 0;
}