A couple of simple functions to calculate the total cost of buying a used car in Ontario (with ability to add a percentage based buffer)

car-calculator.js

const addTax = (price, tax) => price + (price * tax);
const addOntarioTax = (price) => addTax(price, 0.13);
const addLicensingCost = (price) => (price + 20 + 40 + 108);
const addBuffer = (price, buffer = 0) => (price + (price * buffer));
const calculateTotalCost = (price, buffer) => Math.round(addBuffer(addLicensingCost(addOntarioTax(price)), buffer));

module.exports = {
  calculateTotalCost,
};

If you want to buy a car for 10000, then the retail price needs to be ~8500. Once you add the tax and licensing fees it adds up...