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 $84.92   8.873%   $92.455   $92.46   $92.45   $92.50  
  Purchase #2 $196.35   8.736%   $213.5031   $213.50   $213.50   $213.50  
  Purchase #3 $117.45   12.149%   $131.719   $131.72   $131.70   $131.70  
  Purchase #4 $92.44   12.602%   $104.0893   $104.09   $104.10   $104.10  
  Purchase #5 $112.83   8.188%   $122.0685   $122.07   $122.05   $122.10  
  Purchase #6 $194.99   7.283%   $209.1911   $209.19   $209.20   $209.20  
  Purchase #7 $122.69   12.292%   $137.7711   $137.77   $137.75   $137.80  
  7 purchase totals = $921.67       $1,010.7971   $1,010.80   $1,010.75   $1,010.90