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 $53.63   11.268%   $59.673   $59.67   $59.65   $59.70  
  Purchase #2 $131.74   10.137%   $145.0945   $145.09   $145.10   $145.10  
  Purchase #3 $122.63   6.489%   $130.5875   $130.59   $130.60   $130.60  
  Purchase #4 $26.28   7.442%   $28.2358   $28.24   $28.25   $28.20  
  Purchase #5 $63.93   8.853%   $69.5897   $69.59   $69.60   $69.60  
  Purchase #6 $192.39   11.296%   $214.1224   $214.12   $214.10   $214.10  
  Purchase #7 $94.91   11.395%   $105.725   $105.73   $105.75   $105.70  
  7 purchase totals = $685.51       $753.0279   $753.03   $753.05   $753.00