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 $95.26   11.236%   $105.9634   $105.96   $105.95   $106.00  
  Purchase #2 $64.93   5.663%   $68.607   $68.61   $68.60   $68.60  
  Purchase #3 $92.34   10.807%   $102.3192   $102.32   $102.30   $102.30  
  Purchase #4 $243.49   8.105%   $263.2249   $263.22   $263.20   $263.20  
  Purchase #5 $16.45   7.263%   $17.6448   $17.64   $17.65   $17.60  
  Purchase #6 $248.44   5.430%   $261.9303   $261.93   $261.95   $261.90  
  Purchase #7 $42.54   3.644%   $44.0902   $44.09   $44.10   $44.10  
  7 purchase totals = $803.45       $863.7798   $863.77   $863.75   $863.70