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 $233.41   8.267%   $252.706   $252.71   $252.70   $252.70  
  Purchase #2 $248.82   5.764%   $263.162   $263.16   $263.15   $263.20  
  Purchase #3 $69.53   8.496%   $75.4373   $75.44   $75.45   $75.40  
  Purchase #4 $232.39   11.766%   $259.733   $259.73   $259.75   $259.70  
  Purchase #5 $238.80   11.426%   $266.0853   $266.09   $266.10   $266.10  
  Purchase #6 $140.49   7.677%   $151.2754   $151.28   $151.30   $151.30  
  Purchase #7 $180.89   5.369%   $190.602   $190.60   $190.60   $190.60  
  7 purchase totals = $1,344.33       $1,459.0010   $1,459.01   $1,459.05   $1,459.00