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	$49.87	3.245%	$51.4883	$51.49	$51.50	$51.50
Purchase #2	$115.27	10.289%	$127.1301	$127.13	$127.15	$127.10
Purchase #3	$22.55	13.530%	$25.601	$25.60	$25.60	$25.60
Purchase #4	$230.79	10.717%	$255.5238	$255.52	$255.50	$255.50
Purchase #5	$60.98	11.296%	$67.8683	$67.87	$67.85	$67.90
Purchase #6	$144.53	3.717%	$149.9022	$149.90	$149.90	$149.90
Purchase #7	$104.54	13.128%	$118.264	$118.26	$118.25	$118.30
7 purchase totals =	$728.53		$795.7777	$795.77	$795.75	$795.80