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 $84.68   12.455%   $95.2269   $95.23   $95.25   $95.20  
  Purchase #2 $22.94   8.723%   $24.9411   $24.94   $24.95   $24.90  
  Purchase #3 $249.38   6.658%   $265.9837   $265.98   $266.00   $266.00  
  Purchase #4 $197.88   13.481%   $224.5562   $224.56   $224.55   $224.60  
  Purchase #5 $123.34   11.864%   $137.9731   $137.97   $137.95   $138.00  
  Purchase #6 $90.44   5.131%   $95.0805   $95.08   $95.10   $95.10  
  Purchase #7 $144.67   4.798%   $151.6113   $151.61   $151.60   $151.60  
  7 purchase totals = $913.33       $995.3728   $995.37   $995.40   $995.40