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 $81.76   13.315%   $92.6463   $92.65   $92.65   $92.60  
  Purchase #2 $112.47   5.808%   $119.0023   $119.00   $119.00   $119.00  
  Purchase #3 $210.90   7.856%   $227.4683   $227.47   $227.45   $227.50  
  Purchase #4 $25.59   5.729%   $27.0561   $27.06   $27.05   $27.10  
  Purchase #5 $66.61   3.514%   $68.9507   $68.95   $68.95   $69.00  
  Purchase #6 $190.88   3.406%   $197.3814   $197.38   $197.40   $197.40  
  Purchase #7 $185.95   6.289%   $197.6444   $197.64   $197.65   $197.60  
  7 purchase totals = $874.16       $930.1495   $930.15   $930.15   $930.20