Total calculate error

Hello!
I installed the plugin to add a tax for cash on delivery payment.
In checkout page, when I select the payment method, it appears but Total don’t show it with the tax included.

For example:
Product 1 –> 7,60 €
Product 2 –> 13,60 €
Subtotal –> 21,20 €
Shipping —> 3,00 €
Extra charge for cash on delivery –> 5,00 €
Total –> 24,20 €

It should be 29,20 €

How could I solve it?
Thank you so much.

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