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	$214.31	3.639%	$222.1087	$222.11	$222.10	$222.10
Purchase #2	$133.62	13.303%	$151.3955	$151.40	$151.40	$151.40
Purchase #3	$70.95	5.370%	$74.76	$74.76	$74.75	$74.80
Purchase #4	$146.77	5.377%	$154.6618	$154.66	$154.65	$154.70
Purchase #5	$78.95	3.740%	$81.9027	$81.90	$81.90	$81.90
Purchase #6	$118.44	4.499%	$123.7686	$123.77	$123.75	$123.80
Purchase #7	$99.78	11.613%	$111.3675	$111.37	$111.35	$111.40
7 purchase totals =	$862.82		$919.9648	$919.97	$919.90	$920.10