As of version 2.117 you can configure how many decimals will be used and shown for your Sales Price in all the calculations and for the according surcharges you can follow the steps below.
First of all, you should know that you can select up to 9 decimal digits for your sales price. Please decide which value suits best for you.
1. Set Administration Setting
The first step for changing the decimals of your sales price is the setting in the 220.127.116.11 Administration Settings.
After selecting a value between 0 and 9 for the field "Sales Price decimal places" you can proceed with step 2.
Default decimal value
The default value set in this field is 2 decimals.
2. Set Currency Decimals
Please note that the decimals in the Salesforce Currency Setup can be configured to a maximum of 6 decimal places. If you have your Administration settings configured to show 7-9 decimal places, the calculations will take place based on 7-9 decimal places and the results will be shown rounded to a maximum of 6 decimal places in the UI.
To be able to show the decimals selected also in all fields you need to go to Setup > Manage Currencies and select for each Currencies you are working with "Edit".
Afterwards enter the number of decimal places you want to see for the currency fields in Salesforce.
The rounding for all the amounts will still apply to 2 decimals as you can read on this Wiki page: 18.104.22.168 Rounding Alert.