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 $84.66   12.245%   $95.0266   $95.03   $95.05   $95.00  
  Purchase #2 $109.80   11.460%   $122.3831   $122.38   $122.40   $122.40  
  Purchase #3 $86.38   13.167%   $97.7537   $97.75   $97.75   $97.80  
  Purchase #4 $76.68   6.512%   $81.6734   $81.67   $81.65   $81.70  
  Purchase #5 $232.46   13.706%   $264.321   $264.32   $264.30   $264.30  
  Purchase #6 $161.79   11.220%   $179.9428   $179.94   $179.95   $179.90  
  Purchase #7 $61.42   4.422%   $64.136   $64.14   $64.15   $64.10  
  7 purchase totals = $813.19       $905.2366   $905.23   $905.25   $905.20