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 $103.69   10.427%   $114.5018   $114.50   $114.50   $114.50  
  Purchase #2 $63.33   8.475%   $68.6972   $68.70   $68.70   $68.70  
  Purchase #3 $62.34   8.454%   $67.6102   $67.61   $67.60   $67.60  
  Purchase #4 $228.98   11.795%   $255.9882   $255.99   $256.00   $256.00  
  Purchase #5 $164.94   13.431%   $187.0931   $187.09   $187.10   $187.10  
  Purchase #6 $40.75   4.814%   $42.7117   $42.71   $42.70   $42.70  
  Purchase #7 $217.88   6.873%   $232.8549   $232.85   $232.85   $232.90  
  7 purchase totals = $881.91       $969.4571   $969.45   $969.45   $969.50