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 $182.70   7.698%   $196.7642   $196.76   $196.75   $196.80  
  Purchase #2 $103.70   3.212%   $107.0308   $107.03   $107.05   $107.00  
  Purchase #3 $104.68   12.624%   $117.8948   $117.89   $117.90   $117.90  
  Purchase #4 $121.25   9.314%   $132.5432   $132.54   $132.55   $132.50  
  Purchase #5 $51.55   9.781%   $56.5921   $56.59   $56.60   $56.60  
  Purchase #6 $26.46   4.375%   $27.6176   $27.62   $27.60   $27.60  
  Purchase #7 $58.32   12.511%   $65.6164   $65.62   $65.60   $65.60  
  7 purchase totals = $648.66       $704.0591   $704.05   $704.05   $704.00