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 $58.71   8.165%   $63.5037   $63.50   $63.50   $63.50  
  Purchase #2 $232.51   5.559%   $245.4352   $245.44   $245.45   $245.40  
  Purchase #3 $38.44   8.316%   $41.6367   $41.64   $41.65   $41.60  
  Purchase #4 $60.80   6.454%   $64.724   $64.72   $64.70   $64.70  
  Purchase #5 $199.36   12.829%   $224.9359   $224.94   $224.95   $224.90  
  Purchase #6 $192.78   8.206%   $208.5995   $208.60   $208.60   $208.60  
  Purchase #7 $202.60   7.636%   $218.0705   $218.07   $218.05   $218.10  
  7 purchase totals = $985.20       $1,066.9055   $1,066.91   $1,066.90   $1,066.80