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	$128.71	12.225%	$144.4448	$144.44	$144.45	$144.40
Purchase #2	$11.67	12.621%	$13.1429	$13.14	$13.15	$13.10
Purchase #3	$194.32	5.779%	$205.5498	$205.55	$205.55	$205.50
Purchase #4	$243.57	4.844%	$255.3685	$255.37	$255.35	$255.40
Purchase #5	$207.58	10.856%	$230.1149	$230.11	$230.10	$230.10
Purchase #6	$202.95	9.670%	$222.5753	$222.58	$222.60	$222.60
Purchase #7	$213.51	13.748%	$242.8634	$242.86	$242.85	$242.90
7 purchase totals =	$1,202.31		$1,314.0596	$1,314.05	$1,314.05	$1,314.00