Add percent to the fee

Our post is little specific for delivery service.
It charges standard fee of 25 money units + 2.5% of total (for handling money transaction) + weight based shipping rate.
Is there possibility to add fee of 2.5% somewhere? I tried with taxes but its only aplying on delivery cost.

Thanks in ahead

https://wordpress.org/plugins/weight-based-shipping-for-woocommerce/