I need to add a fixed percentage surcharge to all order totals.

Commerce Discount almost meets my needs, using a negative discount value.

The only issue is that the required surcharge is 1.12%, but the percentage discount field in commerce discount records the discount as a decimal number eg 0.01 for 1 percent, and the field type is number_decimal, so it wont record a value of -0.0112 - it rounds the figure to -0.01.

Is there a simple way to add a surcharge like this?

Thanks!