[BUG]: Total cost label prints the cost with 5 digits of precision after the decimal point.

[puterboy]

5 digits of precision in costing is clearly excessive given:

1. The actual power data is only recoreded to 3 digits of precision
2. Energy bills and costs are usually rounded to the penny anyway (2 digits of precision)

Suggest that label use 2 or at most 3 digtis of precision for the cost.