商品成本 = $10
税率 = 5%
编写一个JavaScript函数来计算商品的总成本和适用税费。
function totalCost (cost, taxRate) {
  let total = cost + (cost * taxRate / 100);
  return total;
}
let totalPrice = totalCost(10, 5);
console.log(totalPrice); // 10.5