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	$62.64	3.146%	$64.6107	$64.61	$64.60	$64.60
Purchase #2	$129.91	10.324%	$143.3219	$143.32	$143.30	$143.30
Purchase #3	$212.92	8.847%	$231.757	$231.76	$231.75	$231.80
Purchase #4	$150.37	3.264%	$155.2781	$155.28	$155.30	$155.30
Purchase #5	$225.88	13.400%	$256.1479	$256.15	$256.15	$256.10
Purchase #6	$49.49	10.252%	$54.5637	$54.56	$54.55	$54.60
Purchase #7	$160.96	5.476%	$169.7742	$169.77	$169.75	$169.80
7 purchase totals =	$992.17		$1,075.4535	$1,075.45	$1,075.40	$1,075.50