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	$207.86	13.472%	$235.8629	$235.86	$235.85	$235.90
Purchase #2	$102.77	8.695%	$111.7059	$111.71	$111.70	$111.70
Purchase #3	$105.51	4.535%	$110.2949	$110.29	$110.30	$110.30
Purchase #4	$167.59	3.480%	$173.4221	$173.42	$173.40	$173.40
Purchase #5	$60.56	3.408%	$62.6239	$62.62	$62.60	$62.60
Purchase #6	$71.73	11.754%	$80.1611	$80.16	$80.15	$80.20
Purchase #7	$134.76	3.154%	$139.0103	$139.01	$139.00	$139.00
7 purchase totals =	$850.78		$913.0811	$913.07	$913.00	$913.10