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 $84.79   11.513%   $94.5519   $94.55   $94.55   $94.60  
  Purchase #2 $162.97   12.511%   $183.3592   $183.36   $183.35   $183.40  
  Purchase #3 $231.70   6.220%   $246.1117   $246.11   $246.10   $246.10  
  Purchase #4 $90.99   11.783%   $101.7114   $101.71   $101.70   $101.70  
  Purchase #5 $204.87   11.824%   $229.0938   $229.09   $229.10   $229.10  
  Purchase #6 $187.59   5.215%   $197.3728   $197.37   $197.35   $197.40  
  Purchase #7 $101.78   12.457%   $114.4587   $114.46   $114.45   $114.50  
  7 purchase totals = $1,064.69       $1,166.6595   $1,166.65   $1,166.60   $1,166.80