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 $86.26   7.751%   $92.946   $92.95   $92.95   $92.90  
  Purchase #2 $57.33   13.582%   $65.1166   $65.12   $65.10   $65.10  
  Purchase #3 $140.43   10.395%   $155.0277   $155.03   $155.05   $155.00  
  Purchase #4 $243.88   7.237%   $261.5296   $261.53   $261.55   $261.50  
  Purchase #5 $237.48   6.693%   $253.3745   $253.37   $253.35   $253.40  
  Purchase #6 $89.34   5.773%   $94.4976   $94.50   $94.50   $94.50  
  Purchase #7 $114.77   4.495%   $119.9289   $119.93   $119.95   $119.90  
  7 purchase totals = $969.49       $1,042.4209   $1,042.43   $1,042.45   $1,042.30