exact_change.js

var register = [
    {
			name: "PENNY",
      value: 0.01,
      count: 0
    },
    
    {
			name: "NICKEL",
      value: 0.05,
      count: 0
    },
    
    {
			name: "DIME",
      value: 0.1,
      count: 0
    },
  
    {
			name: "QUARTER",
      value: 0.25,
      count: 0
    },
  
    {
			name: "ONE",
      value: 1,
      count: 0
    },
  
    {
			name: "FIVE",
      value: 5,
      count: 0
    },
  
    {
			name: "TEN",
      value: 10,
      count: 0
    },
  
    {
			name: "TWENTY",
      value: 20,
      count: 0
    },
  
    {
			name: "ONE HUNDRED",
      value: 100,
      count: 0
    }
];

function checkCashRegister(price, cash, cid) {
  var change, total_cash;
  // Here is your change, ma'am.
  
  change = cash - price;
  
  total_cash = cid.reduce(function(sum, x) {
    return sum +x[1];
  }, 0);

  if (change.toFixed(2) === total_cash.toFixed(2)) {
    return "Closed";
  }

  cid.forEach(function(denomination){
		register.forEach(function(wtf, index) {
			if (wtf.name === denomination[0]) {
			register[index].count = Math.ceil(denomination[1] / register[index].value);
			}
		});
  });
  

  register = register.reverse();
  answer = [];

  register.forEach(function(den){
    if (change > den.value) {
      quotient = change / den.value;
      remainder = change % den.value;
      
      used = quotient > den.count ? den.count: quotient;
      change = change - (used * den.value).toFixed(2);
      answer.unshift([den.name, (used * den.value)])
    }
  })

  if (change !== 0 ) {
    return "Insufficient Funds"
  }
  //console.log( JSON.stringify(answer, null, 2));
  return answer;
}

// Example cash-in-drawer array:
// [["PENNY", 1.01],
// ["NICKEL", 2.05],
// ["DIME", 3.10],
// ["QUARTER", 4.25],
// ["ONE", 90.00],
// ["FIVE", 55.00],
// ["TEN", 20.00],
// ["TWENTY", 60.00],
// ["ONE HUNDRED", 100.00]]

//checkCashRegister(19.50, 20.00, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.10], ["QUARTER", 4.25], ["ONE", 90.00], ["FIVE", 55.00], ["TEN", 20.00], ["TWENTY", 60.00], ["ONE HUNDRED", 100.00]]);

checkCashRegister(19.50, 20.00, [["PENNY", 0.50], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]])