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 $213.65   10.436%   $235.9465   $235.95   $235.95   $235.90  
  Purchase #2 $57.90   13.374%   $65.6435   $65.64   $65.65   $65.60  
  Purchase #3 $84.51   4.267%   $88.116   $88.12   $88.10   $88.10  
  Purchase #4 $134.57   10.292%   $148.4199   $148.42   $148.40   $148.40  
  Purchase #5 $224.83   8.695%   $244.379   $244.38   $244.40   $244.40  
  Purchase #6 $200.96   5.308%   $211.627   $211.63   $211.65   $211.60  
  Purchase #7 $248.35   5.159%   $261.1624   $261.16   $261.15   $261.20  
  7 purchase totals = $1,164.77       $1,255.2943   $1,255.30   $1,255.30   $1,255.20