basket.js

'use strict'

let cash = 1000
let tax = 0.01

let basket1 = {
  'Phone': 130,
  'Accessory': 30,
}

let amount = 0

function findMinValue(obj) {
  let min = Infinity
  for (let i in obj) {
    if (obj[i] < min) min = obj[i]
  }
  return min
}

function calcTax(amt) {
  return amt = amt + (amt * tax)
}

function buyAsMuchAsPossible(basket) {
  while (cash > calcTax(findMinValue(basket)) ) {
    for (let i in basket) {
      if (cash > amount + calcTax(basket[i])) {
        amount = amount + basket[i]
        console.log(`Scanned item [${i}: $${basket[i]}]`);
        console.log(`Current Total $${amount.toFixed(2)}`);
      } else console.log(`You don't have $${basket[i]} for a ${i} :(`);
    }
    amount = calcTax(amount)
    cash = cash - amount
  }
  if (amount === 0) console.log(`You can't afford anything!`);
  console.log(`Final Total (inc. Tax) $${amount.toFixed(2)}`);
  console.log(`Cash remaining $${cash.toFixed(2)}`);
}

buyAsMuchAsPossible(basket1)

Generally I get a little bit nervous when I see for in like this line. Not cause it's wrong but because when you iterate through an object with for in it might iterate through it's prototype's properties as well, read more here. That said, there isn't anything wrong with your code because it's just a normal object :)