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 $216.56   8.493%   $234.9524   $234.95   $234.95   $235.00  
  Purchase #2 $248.56   8.778%   $270.3786   $270.38   $270.40   $270.40  
  Purchase #3 $47.72   12.314%   $53.5962   $53.60   $53.60   $53.60  
  Purchase #4 $243.97   4.868%   $255.8465   $255.85   $255.85   $255.80  
  Purchase #5 $224.37   5.314%   $236.293   $236.29   $236.30   $236.30  
  Purchase #6 $146.75   7.549%   $157.8282   $157.83   $157.85   $157.80  
  Purchase #7 $237.49   3.211%   $245.1158   $245.12   $245.10   $245.10  
  7 purchase totals = $1,365.42       $1,454.0107   $1,454.02   $1,454.05   $1,454.00