Error for total

I am getting this error {"total":["must add up correctly to the items, discount, tax and shipping costs"]} for the Mijireh checkout with this plugin on the site https://boarddirection.com.au/services/

It only happens when the book is the only product. I’m not sure if it’s a tax rounding issue, but it doesn’t happen for any of the other products, and the only significant difference I can see is that they’re about 10x the price of the book.

Really need help on this one, please!

https://www.ads-software.com/plugins/easy-digital-downloads-mijireh-checkout/