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 $146.64   4.757%   $153.6157   $153.62   $153.60   $153.60  
  Purchase #2 $199.43   4.159%   $207.7243   $207.72   $207.70   $207.70  
  Purchase #3 $232.26   12.668%   $261.6827   $261.68   $261.70   $261.70  
  Purchase #4 $122.50   9.405%   $134.0211   $134.02   $134.00   $134.00  
  Purchase #5 $231.92   5.231%   $244.0517   $244.05   $244.05   $244.10  
  Purchase #6 $166.73   5.487%   $175.8785   $175.88   $175.90   $175.90  
  Purchase #7 $130.55   11.497%   $145.5593   $145.56   $145.55   $145.60  
  7 purchase totals = $1,230.03       $1,322.5333   $1,322.53   $1,322.50   $1,322.60