Depends what industry you are going into...From my experience, if you are going into something super competitive like finance or law, you will find you def get screened based on your ATAR as well as your uni marks to even get an interview. You will often have to sit psychometric tests as well if you make it past that screening.I can't possibly see why an employer would ask for your ATAR, it is truly is a horrible measure of job suitability. Especially if you consider those jobs that are so 'competitive' that they could theoretically ask you for it, would generally be ones that are academic and require a degree of some sort. Which means that your ATAR would be at least 3 years old, and going back to someones performance 3 years ago would be a horrible indicator of their current academic performance compared to say their uni marks.
Once you get past that screening/HR process its less of an issue, especially when you are being interviewed by someone who actually works in the business. At that point they are just looking for someone they would want to sit next to for 70hours a week.