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 $176.41   11.600%   $196.8736   $196.87   $196.85   $196.90  
  Purchase #2 $77.49   8.686%   $84.2208   $84.22   $84.20   $84.20  
  Purchase #3 $126.39   11.546%   $140.983   $140.98   $141.00   $141.00  
  Purchase #4 $249.40   11.179%   $277.2804   $277.28   $277.30   $277.30  
  Purchase #5 $41.57   13.118%   $47.0232   $47.02   $47.00   $47.00  
  Purchase #6 $114.62   11.353%   $127.6328   $127.63   $127.65   $127.60  
  Purchase #7 $74.48   11.564%   $83.0929   $83.09   $83.10   $83.10  
  7 purchase totals = $860.36       $957.1067   $957.09   $957.10   $957.10