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 $60.84   5.598%   $64.2458   $64.25   $64.25   $64.20  
  Purchase #2 $139.27   4.430%   $145.4397   $145.44   $145.45   $145.40  
  Purchase #3 $127.32   7.134%   $136.403   $136.40   $136.40   $136.40  
  Purchase #4 $8.53   11.565%   $9.5165   $9.52   $9.50   $9.50  
  Purchase #5 $143.37   5.159%   $150.7665   $150.77   $150.75   $150.80  
  Purchase #6 $197.80   3.271%   $204.27   $204.27   $204.25   $204.30  
  Purchase #7 $14.38   9.204%   $15.7035   $15.70   $15.70   $15.70  
  7 purchase totals = $691.51       $726.3450   $726.35   $726.30   $726.30