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 $43.89   4.841%   $46.0147   $46.01   $46.00   $46.00  
  Purchase #2 $151.76   6.863%   $162.1753   $162.18   $162.20   $162.20  
  Purchase #3 $10.50   10.733%   $11.627   $11.63   $11.65   $11.60  
  Purchase #4 $244.46   7.797%   $263.5205   $263.52   $263.50   $263.50  
  Purchase #5 $157.25   6.574%   $167.5876   $167.59   $167.60   $167.60  
  Purchase #6 $138.45   13.338%   $156.9165   $156.92   $156.90   $156.90  
  Purchase #7 $125.55   10.636%   $138.9035   $138.90   $138.90   $138.90  
  7 purchase totals = $871.86       $946.7451   $946.75   $946.75   $946.70