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 $104.99   8.657%   $114.079   $114.08   $114.10   $114.10  
  Purchase #2 $195.43   11.348%   $217.6074   $217.61   $217.60   $217.60  
  Purchase #3 $77.41   8.628%   $84.0889   $84.09   $84.10   $84.10  
  Purchase #4 $207.73   13.254%   $235.2625   $235.26   $235.25   $235.30  
  Purchase #5 $149.63   6.854%   $159.8856   $159.89   $159.90   $159.90  
  Purchase #6 $111.73   5.137%   $117.4696   $117.47   $117.45   $117.50  
  Purchase #7 $84.56   12.616%   $95.2281   $95.23   $95.25   $95.20  
  7 purchase totals = $931.48       $1,023.6211   $1,023.63   $1,023.65   $1,023.70