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 $209.36   13.661%   $237.9607   $237.96   $237.95   $238.00  
  Purchase #2 $199.53   13.318%   $226.1034   $226.10   $226.10   $226.10  
  Purchase #3 $78.65   4.787%   $82.415   $82.42   $82.40   $82.40  
  Purchase #4 $228.82   12.800%   $258.109   $258.11   $258.10   $258.10  
  Purchase #5 $228.34   3.314%   $235.9072   $235.91   $235.90   $235.90  
  Purchase #6 $206.44   4.114%   $214.9329   $214.93   $214.95   $214.90  
  Purchase #7 $226.78   6.446%   $241.3982   $241.40   $241.40   $241.40  
  7 purchase totals = $1,377.92       $1,496.8264   $1,496.83   $1,496.80   $1,496.80