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	$227.72	7.257%	$244.2456	$244.25	$244.25	$244.20
Purchase #2	$18.77	12.621%	$21.139	$21.14	$21.15	$21.10
Purchase #3	$210.72	5.237%	$221.7554	$221.76	$221.75	$221.80
Purchase #4	$135.89	5.566%	$143.4536	$143.45	$143.45	$143.50
Purchase #5	$151.39	8.482%	$164.2309	$164.23	$164.25	$164.20
Purchase #6	$104.37	6.604%	$111.2626	$111.26	$111.25	$111.30
Purchase #7	$32.32	5.613%	$34.1341	$34.13	$34.15	$34.10
7 purchase totals =	$881.18		$940.2212	$940.22	$940.25	$940.20