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 $197.91   4.725%   $207.2612   $207.26   $207.25   $207.30  
  Purchase #2 $194.88   5.522%   $205.6413   $205.64   $205.65   $205.60  
  Purchase #3 $221.78   11.757%   $247.8547   $247.85   $247.85   $247.90  
  Purchase #4 $61.39   11.814%   $68.6426   $68.64   $68.65   $68.60  
  Purchase #5 $68.25   7.684%   $73.4943   $73.49   $73.50   $73.50  
  Purchase #6 $48.27   4.546%   $50.4644   $50.46   $50.45   $50.50  
  Purchase #7 $114.25   7.727%   $123.0781   $123.08   $123.10   $123.10  
  7 purchase totals = $906.73       $976.4366   $976.42   $976.45   $976.50