Using calculations and conditions for the total price

I'm trying to make it where each item selected changed the total price for the service. Is there a function or widget that helps me with that?

You can have this kind of function by using the Form Calculation widget and Update/Calculate Field Conditions. Here's a demo form from the calculation guide: .

Here are some helpful guides:
https://www.jotform.com/help/259-How-to-Perform-Calculation-in-the-Form
https://www.jotform.com/help/286-How-to-Pass-Field-Value-to-Another-Field

 

Hope that helps. If you have any questions, let us know. Thank you.