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	$97.31	11.143%	$108.1533	$108.15	$108.15	$108.20
Purchase #2	$127.94	3.864%	$132.8836	$132.88	$132.90	$132.90
Purchase #3	$166.52	11.831%	$186.221	$186.22	$186.20	$186.20
Purchase #4	$99.88	3.348%	$103.224	$103.22	$103.20	$103.20
Purchase #5	$182.83	4.125%	$190.3717	$190.37	$190.35	$190.40
Purchase #6	$157.28	10.243%	$173.3902	$173.39	$173.40	$173.40
Purchase #7	$246.34	6.730%	$262.9187	$262.92	$262.90	$262.90
7 purchase totals =	$1,078.10		$1,157.1625	$1,157.15	$1,157.10	$1,157.20