However, having two sets of books as many businesses do really works against them in the long run. What happens if you want to sell? You really can't sell for the price your business is worth unless you can show the true profit made. And when you take cash out of the business, it really has to be spent on non-essentials such as holidays or grog, instead of what the business truly needs to make it more efficient.
Tax evasion is easy for the ATO to see; they have only to compare a similar business with yours to see what the income should be. Keeping up with the cash flow by paying all the GST, superannuation and everything else that must be paid will ensure that you sleep better at nights and your business runs more smoothly.
If you can't keep up, get some like finding to take the headache out of your accounting woes.