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 $86.53   11.510%   $96.4896   $96.49   $96.50   $96.50  
  Purchase #2 $211.43   11.758%   $236.2899   $236.29   $236.30   $236.30  
  Purchase #3 $176.49   4.198%   $183.8991   $183.90   $183.90   $183.90  
  Purchase #4 $62.44   13.102%   $70.6209   $70.62   $70.60   $70.60  
  Purchase #5 $121.44   10.622%   $134.3394   $134.34   $134.35   $134.30  
  Purchase #6 $221.82   10.755%   $245.6767   $245.68   $245.70   $245.70  
  Purchase #7 $72.57   8.469%   $78.716   $78.72   $78.70   $78.70  
  7 purchase totals = $952.72       $1,046.0316   $1,046.04   $1,046.05   $1,046.00