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 $211.47   7.110%   $226.5055   $226.51   $226.50   $226.50  
  Purchase #2 $201.54   10.287%   $222.2724   $222.27   $222.25   $222.30  
  Purchase #3 $146.40   10.827%   $162.2507   $162.25   $162.25   $162.30  
  Purchase #4 $214.88   7.792%   $231.6234   $231.62   $231.60   $231.60  
  Purchase #5 $70.95   3.262%   $73.2644   $73.26   $73.25   $73.30  
  Purchase #6 $122.71   11.556%   $136.8904   $136.89   $136.90   $136.90  
  Purchase #7 $217.59   11.537%   $242.6934   $242.69   $242.70   $242.70  
  7 purchase totals = $1,185.54       $1,295.5002   $1,295.49   $1,295.45   $1,295.60