Rounded shopping budgets: use the receipt after the purchase
By Erik Nilsen · Kroni3 min read
Rounding prices can make a shopping budget easier to calculate mentally. An estimate and an actual payment serve different purposes, though. The estimate helps your child before buying; the receipt shows what to record afterwards.
Round upwards when planning
In a hypothetical example, your child selects three small items costing 19.90, 24.50 and 35.20 units. They have 85 units available. These are arbitrary teaching prices, and the example assumes the stated decimal amounts are paid without checkout rounding.
For a quick estimate, use 20, 25 and 36 units. The total is 81. Your child therefore expects to keep at least 85 − 81 = 4 units, provided no other costs are added. Each price has been rounded upwards rather than all prices being rounded to the nearest ten.
The exact total is 19.90 + 24.50 + 35.20 = 79.60 units. After payment, your child has 85 − 79.60 = 5.40 units left. The difference between estimate and receipt is 81 − 79.60 = 1.40 units. That difference is money never spent, rather than a new bonus.
Replace the estimate with the actual amount
Write the estimate on the shopping list but label it “before buying”. At home, your child can write the receipt total alongside it. Use the amount actually paid in your family money record. Do not deduct both the estimate and the receipt total.
A realistic snag is that one product has a different checkout price or another item is substituted. The old estimate cannot establish the final payment. Look at the receipt, check its individual lines, and ask the shop about any uncertainty before finishing the calculation.
If your family normally records only whole units, decide who covers the difference. An agreed deduction of 80 units is different from claiming that the purchase cost exactly 80. Write the rule clearly, especially if small differences occur frequently.
Practise again with the same list without buying anything. Your child can estimate first and calculate exactly afterwards. They can also circle which of the three prices created the largest rounding gap and explain why. Ask your family: “Which number did we use to plan, and which number tells us what was actually paid?”
Carry the calculation into your family agreement
Kroni can keep track of your child's virtual balance. The app does not transfer money, so any actual purchase is paid for outside it. Agree on what you will record, then check the amount with your child afterwards. Do not deduct a possible cost as though the purchase had already happened. Read about allowance in Kroni.
