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 $48.95   9.503%   $53.6017   $53.60   $53.60   $53.60  
  Purchase #2 $62.37   4.683%   $65.2908   $65.29   $65.30   $65.30  
  Purchase #3 $199.25   5.557%   $210.3223   $210.32   $210.30   $210.30  
  Purchase #4 $68.69   13.167%   $77.7344   $77.73   $77.75   $77.70  
  Purchase #5 $165.89   9.830%   $182.197   $182.20   $182.20   $182.20  
  Purchase #6 $125.44   13.534%   $142.417   $142.42   $142.40   $142.40  
  Purchase #7 $71.62   6.489%   $76.2674   $76.27   $76.25   $76.30  
  7 purchase totals = $742.21       $807.8306   $807.83   $807.80   $807.80