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 $208.95   7.280%   $224.1616   $224.16   $224.15   $224.20  
  Purchase #2 $42.57   9.741%   $46.7167   $46.72   $46.70   $46.70  
  Purchase #3 $176.70   5.185%   $185.8619   $185.86   $185.85   $185.90  
  Purchase #4 $120.39   11.556%   $134.3023   $134.30   $134.30   $134.30  
  Purchase #5 $226.69   3.195%   $233.9327   $233.93   $233.95   $233.90  
  Purchase #6 $121.37   12.775%   $136.875   $136.88   $136.90   $136.90  
  Purchase #7 $159.50   3.388%   $164.9039   $164.90   $164.90   $164.90  
  7 purchase totals = $1,056.17       $1,126.7541   $1,126.75   $1,126.75   $1,126.80