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 $161.66   9.271%   $176.6475   $176.65   $176.65   $176.60  
  Purchase #2 $168.91   13.159%   $191.1369   $191.14   $191.15   $191.10  
  Purchase #3 $9.73   13.779%   $11.0707   $11.07   $11.05   $11.10  
  Purchase #4 $81.87   13.480%   $92.9061   $92.91   $92.90   $92.90  
  Purchase #5 $97.32   5.733%   $102.8994   $102.90   $102.90   $102.90  
  Purchase #6 $44.72   9.472%   $48.9559   $48.96   $48.95   $49.00  
  Purchase #7 $195.34   7.226%   $209.4553   $209.46   $209.45   $209.50  
  7 purchase totals = $759.55       $833.0718   $833.09   $833.05   $833.10