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 $174.63   7.701%   $188.0783   $188.08   $188.10   $188.10  
  Purchase #2 $248.49   6.865%   $265.5488   $265.55   $265.55   $265.50  
  Purchase #3 $215.86   8.837%   $234.9355   $234.94   $234.95   $234.90  
  Purchase #4 $204.83   10.771%   $226.8922   $226.89   $226.90   $226.90  
  Purchase #5 $235.99   10.726%   $261.3023   $261.30   $261.30   $261.30  
  Purchase #6 $57.70   13.707%   $65.6089   $65.61   $65.60   $65.60  
  Purchase #7 $226.75   11.552%   $252.9442   $252.94   $252.95   $252.90  
  7 purchase totals = $1,364.25       $1,495.3102   $1,495.31   $1,495.35   $1,495.20