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 $88.97   7.872%   $95.9737   $95.97   $95.95   $96.00  
  Purchase #2 $30.30   8.731%   $32.9455   $32.95   $32.95   $32.90  
  Purchase #3 $89.43   7.240%   $95.9047   $95.90   $95.90   $95.90  
  Purchase #4 $237.79   11.602%   $265.3784   $265.38   $265.40   $265.40  
  Purchase #5 $133.67   4.739%   $140.0046   $140.00   $140.00   $140.00  
  Purchase #6 $193.78   10.740%   $214.592   $214.59   $214.60   $214.60  
  Purchase #7 $94.75   3.788%   $98.3391   $98.34   $98.35   $98.30  
  7 purchase totals = $868.69       $943.1380   $943.13   $943.15   $943.10