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 $41.78   4.399%   $43.6179   $43.62   $43.60   $43.60  
  Purchase #2 $226.58   7.788%   $244.2261   $244.23   $244.25   $244.20  
  Purchase #3 $162.53   3.548%   $168.2966   $168.30   $168.30   $168.30  
  Purchase #4 $109.75   10.398%   $121.1618   $121.16   $121.15   $121.20  
  Purchase #5 $45.71   9.433%   $50.0218   $50.02   $50.00   $50.00  
  Purchase #6 $233.84   4.440%   $244.2225   $244.22   $244.20   $244.20  
  Purchase #7 $76.72   9.448%   $83.9685   $83.97   $83.95   $84.00  
  7 purchase totals = $896.91       $955.5152   $955.52   $955.45   $955.50