Repeater Field for Calculations and Groups of Calculations

My use case is for construction and I want the users to be able to add a new item which would consist of four columns: Description, Qty, Unit, Rate, Total where the total - Qty x Rate. I need to be able to repeat this entire row. Additionally I would like to be able sum all totals if possible or create sub totals which would be carried forward and create a grand total of all the sub totals.