Commissions earned for domestic travel services are subject to sales tax (such as GST / VAT). Commission earned for international travel or for travel products in other countries are not subject to sales tax.

On your weekly reports from Hero you'll see these items split out, so the sales tax applicable to each week's invoice is only applied to the commission items for domestic products.

Here's an example:

Your commission income for domestic sales includes sales tax, so when filing tax returns you'll need to account for it as GST-inclusive earnings. 

This would be the same as earning commissions from the sale of domestic products via any other method.
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There's a good article on the ATO website which relates to this:

https://www.ato.gov.au/business/GST/in-detail/your-industry/travel-and-tourism/gst-and-international-travel/?anchor=Commissions#Commissions