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 $192.65   4.137%   $200.6199   $200.62   $200.60   $200.60  
  Purchase #2 $146.27   11.143%   $162.5689   $162.57   $162.55   $162.60  
  Purchase #3 $130.99   11.507%   $146.063   $146.06   $146.05   $146.10  
  Purchase #4 $83.47   8.347%   $90.4372   $90.44   $90.45   $90.40  
  Purchase #5 $51.98   9.334%   $56.8318   $56.83   $56.85   $56.80  
  Purchase #6 $208.63   4.490%   $217.9975   $218.00   $218.00   $218.00  
  Purchase #7 $18.95   8.449%   $20.5511   $20.55   $20.55   $20.60  
  7 purchase totals = $832.94       $895.0694   $895.07   $895.05   $895.10