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	$82.51	9.258%	$90.1488	$90.15	$90.15	$90.10
Purchase #2	$44.60	13.347%	$50.5528	$50.55	$50.55	$50.60
Purchase #3	$53.59	10.818%	$59.3874	$59.39	$59.40	$59.40
Purchase #4	$157.26	10.467%	$173.7204	$173.72	$173.70	$173.70
Purchase #5	$134.84	5.168%	$141.8085	$141.81	$141.80	$141.80
Purchase #6	$158.43	9.272%	$173.1196	$173.12	$173.10	$173.10
Purchase #7	$238.99	11.111%	$265.5442	$265.54	$265.55	$265.50
7 purchase totals =	$870.22		$954.2817	$954.28	$954.25	$954.20