Such a tax would be like re-implementing tariff barriers. It could certainly be interpreted that way. Big business is not calling for new trade barriers is it? It has taken half a century to reduce barriers in the car industry. Even now some obstacles to free trade remain in motor vehicle production.
Australian businesses have to lift their game. Go into a department store and try to find someone to give assistance. You can't find anybody! Staff has been cut to ridiculously low levels.
If you do find a lower price for a product on the Internet from a company overseas there is still the post and packaging cost to add on. When you do your sums you are only a few dollars better off. People shop online mainly for convenience. For example, in the US a Samsung fridge sells for $1,385. In Australia the same refrigerator goes for $2,099. People would not buy it online because of the cost and problems of getting it to Australia. Anyway, the US fridge will not run on 240V electricity supply.
The real issue is Australian business had it too good. Before the Internet, retailers had a closed market. Now trade is becoming global and they don't like it. It is well known that Woolworths and Coles keep their prices high where branches are located in "exclusive" parts of cities. It is about time this practice stopped.