Why is the tax rate calculation incorrect in my online store?

[Davo3]

Hello,

I have set up my store to collect tax in Australia. Tax rate is 10%.

However, the tax rate calculated at checkout is incorrect.

All our prices need to include tax. 

I have experimented with unticking the box "All prices include tax", and that does the calculations correctly.

Can you please let me know if this is a bug in Shopify? Or have I missed a setting somewhere?

Thanks

[Davo3]

I have been informed that this calculation is correct.