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 $46.75   3.605%   $48.4353   $48.44   $48.45   $48.40  
  Purchase #2 $210.86   3.696%   $218.6534   $218.65   $218.65   $218.70  
  Purchase #3 $100.71   11.484%   $112.2755   $112.28   $112.30   $112.30  
  Purchase #4 $199.99   8.776%   $217.5411   $217.54   $217.55   $217.50  
  Purchase #5 $11.46   7.538%   $12.3239   $12.32   $12.30   $12.30  
  Purchase #6 $59.62   4.217%   $62.1342   $62.13   $62.15   $62.10  
  Purchase #7 $216.78   3.497%   $224.3608   $224.36   $224.35   $224.40  
  7 purchase totals = $846.17       $895.7242   $895.72   $895.75   $895.70