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	$127.30	11.607%	$142.0757	$142.08	$142.10	$142.10
Purchase #2	$48.54	3.538%	$50.2573	$50.26	$50.25	$50.30
Purchase #3	$33.41	4.710%	$34.9836	$34.98	$35.00	$35.00
Purchase #4	$156.59	10.414%	$172.8973	$172.90	$172.90	$172.90
Purchase #5	$46.60	13.171%	$52.7377	$52.74	$52.75	$52.70
Purchase #6	$16.51	12.352%	$18.5493	$18.55	$18.55	$18.50
Purchase #7	$154.38	12.334%	$173.4212	$173.42	$173.40	$173.40
7 purchase totals =	$583.33		$644.9221	$644.93	$644.95	$644.90