Rounding is a way of making a number less exact, but easier to do calculations with.

We can round numbers to the nearest 10, the nearest 100, the nearest 1000 and so on.

When rounding a number to a power of ten, we follow these rules:

• If the digit after the one you want to keep is bigger than or equal to \(5\), increase the digit you want to keep by \(1\) (round up).
• If the digit after the one you want to keep is smaller than \(5\), leave the digit you want to keep as it is (round down)
• Replace all digits after the one you want to keep by zeroes.

For example, \(67\) rounded (up) to the nearest ten is \(70\), and \(63\) rounded (down) to the nearest ten is \(60\).

Because we no longer have \(1\) and \(2\) cent pieces in Australia, we have to round our money to the nearest \(5 \text{cents}\). The rules for doing this are as follows:

• If the unit cents value is less than or equal to \(2\), replace the unit cents value by \(0\).
• If the unit cents value is greater than or equal to \(3\), but less than or equal to \(5\), replace the unit cents value by \(5\).
• If the unit cents value is greater than or equal to \(5\), but less than or equal to \(7\), replace the unit cents value by \(5\).
• If the unit cents value is greater than or equal to \(8\), increase the ten cents value by \(1\) and replace the unit cents value by \(0\).

For example, \(\$1.62\) rounds down to \($1.60\), \(\$1.63\) rounds up to \(\$1.65\), \(\$1.66\) rounds down to \(\$1.65\) and \(\$1.68\) rounds up to \($1.70\).