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 $201.70   6.218%   $214.2417   $214.24   $214.25   $214.20  
  Purchase #2 $148.99   6.377%   $158.4911   $158.49   $158.50   $158.50  
  Purchase #3 $203.49   3.342%   $210.2906   $210.29   $210.30   $210.30  
  Purchase #4 $225.99   4.550%   $236.2725   $236.27   $236.25   $236.30  
  Purchase #5 $186.75   12.534%   $210.1572   $210.16   $210.15   $210.20  
  Purchase #6 $190.70   8.272%   $206.4747   $206.47   $206.45   $206.50  
  Purchase #7 $128.86   13.493%   $146.2471   $146.25   $146.25   $146.20  
  7 purchase totals = $1,286.48       $1,382.1749   $1,382.17   $1,382.15   $1,382.20