Approximation-tolerant applications give a system designer the possibility to improve traditional design values by slightly decreasing the quality of result. Approximate computing methods introduced for various system layers present the right tools to exploit this potential. However, finding a suitable tuning for a set of methods during design or run time according to the constraints and the system state is tough. Therefore, this paper presents an approach that leads to a transparent view on different approximation methods. This transparent and abstract view can be exploited by tuning approaches to find suitable parameter settings for the current purpose. Furthermore, the presented approach takes multiple objectives and conventional methods, which influence traditional design values, into account. Besides this novel representation approach, this paper introduces a first tuning approach exploiting the presented approach.