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 $88.67   11.211%   $98.6108   $98.61   $98.60   $98.60  
  Purchase #2 $41.53   9.453%   $45.4558   $45.46   $45.45   $45.50  
  Purchase #3 $123.36   10.698%   $136.5571   $136.56   $136.55   $136.60  
  Purchase #4 $219.84   11.713%   $245.5899   $245.59   $245.60   $245.60  
  Purchase #5 $89.88   5.434%   $94.7641   $94.76   $94.75   $94.80  
  Purchase #6 $228.30   3.665%   $236.6672   $236.67   $236.65   $236.70  
  Purchase #7 $235.56   10.338%   $259.9122   $259.91   $259.90   $259.90  
  7 purchase totals = $1,027.14       $1,117.5571   $1,117.56   $1,117.50   $1,117.70