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 $86.72   9.487%   $94.9471   $94.95   $94.95   $94.90  
  Purchase #2 $169.66   9.819%   $186.3189   $186.32   $186.30   $186.30  
  Purchase #3 $21.94   6.104%   $23.2792   $23.28   $23.30   $23.30  
  Purchase #4 $79.36   7.131%   $85.0192   $85.02   $85.00   $85.00  
  Purchase #5 $205.85   7.418%   $221.12   $221.12   $221.10   $221.10  
  Purchase #6 $235.37   6.468%   $250.5937   $250.59   $250.60   $250.60  
  Purchase #7 $244.60   6.771%   $261.1619   $261.16   $261.15   $261.20  
  7 purchase totals = $1,043.50       $1,122.4400   $1,122.44   $1,122.40   $1,122.40