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 $91.32   5.577%   $96.4129   $96.41   $96.40   $96.40  
  Purchase #2 $246.84   5.335%   $260.0089   $260.01   $260.00   $260.00  
  Purchase #3 $192.86   3.581%   $199.7663   $199.77   $199.75   $199.80  
  Purchase #4 $40.71   10.763%   $45.0916   $45.09   $45.10   $45.10  
  Purchase #5 $63.89   6.703%   $68.1725   $68.17   $68.15   $68.20  
  Purchase #6 $215.46   10.666%   $238.441   $238.44   $238.45   $238.40  
  Purchase #7 $242.95   3.565%   $251.6112   $251.61   $251.60   $251.60  
  7 purchase totals = $1,094.03       $1,159.5044   $1,159.50   $1,159.45   $1,159.50