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	$11.78	11.844%	$13.1752	$13.18	$13.20	$13.20
Purchase #2	$237.78	7.482%	$255.5707	$255.57	$255.55	$255.60
Purchase #3	$166.40	5.131%	$174.938	$174.94	$174.95	$174.90
Purchase #4	$50.82	3.373%	$52.5342	$52.53	$52.55	$52.50
Purchase #5	$214.87	12.382%	$241.4752	$241.48	$241.50	$241.50
Purchase #6	$163.65	5.795%	$173.1335	$173.13	$173.15	$173.10
Purchase #7	$97.83	4.729%	$102.4564	$102.46	$102.45	$102.50
7 purchase totals =	$943.13		$1,013.2832	$1,013.29	$1,013.35	$1,013.30