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 $24.86   5.283%   $26.1734   $26.17   $26.15   $26.20  
  Purchase #2 $210.25   5.682%   $222.1964   $222.20   $222.20   $222.20  
  Purchase #3 $42.87   5.836%   $45.3719   $45.37   $45.35   $45.40  
  Purchase #4 $178.64   5.763%   $188.935   $188.94   $188.95   $188.90  
  Purchase #5 $176.93   8.238%   $191.5055   $191.51   $191.50   $191.50  
  Purchase #6 $133.40   8.399%   $144.6043   $144.60   $144.60   $144.60  
  Purchase #7 $61.64   11.478%   $68.715   $68.72   $68.70   $68.70  
  7 purchase totals = $828.59       $887.5015   $887.51   $887.45   $887.50