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 $48.25   9.458%   $52.8135   $52.81   $52.80   $52.80  
  Purchase #2 $29.97   5.419%   $31.5941   $31.59   $31.60   $31.60  
  Purchase #3 $116.81   7.545%   $125.6233   $125.62   $125.60   $125.60  
  Purchase #4 $72.42   7.195%   $77.6306   $77.63   $77.65   $77.60  
  Purchase #5 $95.49   6.806%   $101.989   $101.99   $102.00   $102.00  
  Purchase #6 $10.89   13.872%   $12.4007   $12.40   $12.40   $12.40  
  Purchase #7 $59.40   11.277%   $66.0985   $66.10   $66.10   $66.10  
  7 purchase totals = $433.23       $468.1497   $468.14   $468.15   $468.10