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 $44.42   5.607%   $46.9106   $46.91   $46.90   $46.90  
  Purchase #2 $165.44   10.379%   $182.611   $182.61   $182.60   $182.60  
  Purchase #3 $130.49   8.815%   $141.9927   $141.99   $142.00   $142.00  
  Purchase #4 $208.97   4.253%   $217.8575   $217.86   $217.85   $217.90  
  Purchase #5 $128.83   4.163%   $134.1932   $134.19   $134.20   $134.20  
  Purchase #6 $88.63   4.118%   $92.2798   $92.28   $92.30   $92.30  
  Purchase #7 $197.47   6.596%   $210.4951   $210.50   $210.50   $210.50  
  7 purchase totals = $964.25       $1,026.3399   $1,026.34   $1,026.35   $1,026.40