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 $208.45   12.864%   $235.265   $235.27   $235.25   $235.30  
  Purchase #2 $168.87   3.613%   $174.9713   $174.97   $174.95   $175.00  
  Purchase #3 $65.53   12.140%   $73.4853   $73.49   $73.50   $73.50  
  Purchase #4 $87.82   10.510%   $97.0499   $97.05   $97.05   $97.00  
  Purchase #5 $47.84   7.402%   $51.3811   $51.38   $51.40   $51.40  
  Purchase #6 $149.46   5.393%   $157.5204   $157.52   $157.50   $157.50  
  Purchase #7 $153.50   9.670%   $168.3435   $168.34   $168.35   $168.30  
  7 purchase totals = $881.47       $958.0165   $958.02   $958.00   $958.00