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	$160.95	7.680%	$173.311	$173.31	$173.30	$173.30
Purchase #2	$59.81	11.847%	$66.8957	$66.90	$66.90	$66.90
Purchase #3	$19.32	5.705%	$20.4222	$20.42	$20.40	$20.40
Purchase #4	$50.65	4.872%	$53.1177	$53.12	$53.10	$53.10
Purchase #5	$178.65	7.421%	$191.9076	$191.91	$191.90	$191.90
Purchase #6	$137.39	5.337%	$144.7225	$144.72	$144.70	$144.70
Purchase #7	$208.73	10.335%	$230.3022	$230.30	$230.30	$230.30
7 purchase totals =	$815.50		$880.6789	$880.68	$880.60	$880.60