Value Added Tax is a sales tax added on consumer goods and services in many countries.
When VAT is added to an item or service, the final total may include a fraction of a monetary unit: for example, it may come to £35.234. If this is the case, the price must be rounded UP or DOWN to pay the taxation authority the correct amount.
This can vary by country, but in the UK the price is rounded DOWN to the nearest whole penny.
You have purchased an item and the final price including VAT is £5.234. Obviously it's not possible to pay that amount as currency only goes to 2 decimal places, not 3.
Firstly, write down the amount on a piece of paper and then draw a line to separate the 3 and 4:
Total including VAT: £5.23|4
Now, since VAT rounding in the UK requires rounding DOWN to the nearest penny, simply get rid of the 4:
Total rounded down: £5.23
This can be applied to any price that ends up with an odd fraction, eg:
£1,345.373 = £1,345.37|3 = £1,345.37