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	$248.92	13.476%	$282.4645	$282.46	$282.45	$282.50
Purchase #2	$81.28	4.153%	$84.6556	$84.66	$84.65	$84.70
Purchase #3	$54.89	8.251%	$59.419	$59.42	$59.40	$59.40
Purchase #4	$83.81	10.539%	$92.6427	$92.64	$92.65	$92.60
Purchase #5	$85.94	9.868%	$94.4206	$94.42	$94.40	$94.40
Purchase #6	$49.52	7.301%	$53.1355	$53.14	$53.15	$53.10
Purchase #7	$22.49	13.198%	$25.4582	$25.46	$25.45	$25.50
7 purchase totals =	$626.85		$692.1961	$692.20	$692.15	$692.20