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 $200.89   3.699%   $208.3209   $208.32   $208.30   $208.30  
  Purchase #2 $236.72   9.773%   $259.8546   $259.85   $259.85   $259.90  
  Purchase #3 $231.91   4.153%   $241.5412   $241.54   $241.55   $241.50  
  Purchase #4 $52.86   11.840%   $59.1186   $59.12   $59.10   $59.10  
  Purchase #5 $218.67   8.781%   $237.8714   $237.87   $237.85   $237.90  
  Purchase #6 $235.92   10.857%   $261.5338   $261.53   $261.55   $261.50  
  Purchase #7 $179.74   8.566%   $195.1365   $195.14   $195.15   $195.10  
  7 purchase totals = $1,356.71       $1,463.3770   $1,463.37   $1,463.35   $1,463.30