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 $208.32   11.188%   $231.6268   $231.63   $231.65   $231.60  
  Purchase #2 $114.42   6.332%   $121.6651   $121.67   $121.65   $121.70  
  Purchase #3 $17.71   4.520%   $18.5105   $18.51   $18.50   $18.50  
  Purchase #4 $191.42   5.783%   $202.4898   $202.49   $202.50   $202.50  
  Purchase #5 $171.37   8.734%   $186.3375   $186.34   $186.35   $186.30  
  Purchase #6 $135.63   6.435%   $144.3578   $144.36   $144.35   $144.40  
  Purchase #7 $183.76   3.143%   $189.5356   $189.54   $189.55   $189.50  
  7 purchase totals = $1,022.63       $1,094.5231   $1,094.54   $1,094.55   $1,094.50