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	$85.92	5.401%	$90.5605	$90.56	$90.55	$90.60
Purchase #2	$170.31	11.747%	$190.3163	$190.32	$190.30	$190.30
Purchase #3	$52.58	10.615%	$58.1614	$58.16	$58.15	$58.20
Purchase #4	$111.41	3.614%	$115.4364	$115.44	$115.45	$115.40
Purchase #5	$127.53	12.518%	$143.4942	$143.49	$143.50	$143.50
Purchase #6	$211.67	4.863%	$221.9635	$221.96	$221.95	$222.00
Purchase #7	$214.65	12.555%	$241.5993	$241.60	$241.60	$241.60
7 purchase totals =	$974.07		$1,061.5316	$1,061.53	$1,061.50	$1,061.60