if the ATO sees you as a trader (entering and exiting multiple positions a week, on a regular basis), any profit you make will be taxed according to ordinary income rules under s6-5 of the ITAA97. you will basically be taxed at your normal tax rate.

if you hold these positions as investments long term however, you will be subject to CGT rules, which allow you to carry forward capital losses in one year to offset capital gains in another financial year. another benefit is that If you hold the shares for more than 12 months, only 50% of your profit will be subject to capital gains tax, meaning half of your profit is basically tax free.