initial total prototyped for sell of multiple items
implemented initial display item method
replaced hardcoded currencies with display_item usage
implemented total display
salesystem to use display total functionality
basic total calculation implemented
reworked multiple item sale, better selfdocumentation
stopped mixing double and single quotes, only single quotes from now on
refactoring, split one and variable amount of products tests
added support for tax display, no support for total calc. with tax yet
added support for tax (!only) calculation by price and type
supporting tax calculations for total purchase display