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 $114.63   9.681%   $125.7273   $125.73   $125.75   $125.70  
  Purchase #2 $86.50   8.774%   $94.0895   $94.09   $94.10   $94.10  
  Purchase #3 $216.47   12.253%   $242.9941   $242.99   $243.00   $243.00  
  Purchase #4 $101.77   7.690%   $109.5961   $109.60   $109.60   $109.60  
  Purchase #5 $83.47   6.551%   $88.9381   $88.94   $88.95   $88.90  
  Purchase #6 $175.98   11.594%   $196.3831   $196.38   $196.40   $196.40  
  Purchase #7 $96.61   7.805%   $104.1504   $104.15   $104.15   $104.20  
  7 purchase totals = $875.43       $961.8786   $961.88   $961.95   $961.90