Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $180.38   7.563%   $194.0221   $194.02   $194.00   $194.00  
  Purchase #2 $168.37   10.838%   $186.6179   $186.62   $186.60   $186.60  
  Purchase #3 $242.60   11.153%   $269.6572   $269.66   $269.65   $269.70  
  Purchase #4 $8.52   8.738%   $9.2645   $9.26   $9.25   $9.30  
  Purchase #5 $118.66   6.733%   $126.6494   $126.65   $126.65   $126.60  
  Purchase #6 $43.41   11.238%   $48.2884   $48.29   $48.30   $48.30  
  Purchase #7 $101.45   8.474%   $110.0469   $110.05   $110.05   $110.00  
  7 purchase totals = $863.39       $944.5464   $944.55   $944.50   $944.50