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	$38.48	12.709%	$43.3704	$43.37	$43.35	$43.40
Purchase #2	$38.44	3.325%	$39.7181	$39.72	$39.70	$39.70
Purchase #3	$201.65	10.277%	$222.3736	$222.37	$222.35	$222.40
Purchase #4	$210.89	4.320%	$220.0004	$220.00	$220.00	$220.00
Purchase #5	$47.27	12.864%	$53.3508	$53.35	$53.35	$53.40
Purchase #6	$163.67	5.448%	$172.5867	$172.59	$172.60	$172.60
Purchase #7	$119.83	12.225%	$134.4792	$134.48	$134.50	$134.50
7 purchase totals =	$820.23		$885.8792	$885.88	$885.85	$886.00