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	$222.58	3.508%	$230.3881	$230.39	$230.40	$230.40
Purchase #2	$232.64	7.680%	$250.5068	$250.51	$250.50	$250.50
Purchase #3	$33.97	11.381%	$37.8361	$37.84	$37.85	$37.80
Purchase #4	$68.60	11.333%	$76.3744	$76.37	$76.35	$76.40
Purchase #5	$176.37	11.163%	$196.0582	$196.06	$196.05	$196.10
Purchase #6	$110.27	5.438%	$116.2665	$116.27	$116.25	$116.30
Purchase #7	$48.76	6.168%	$51.7675	$51.77	$51.75	$51.80
7 purchase totals =	$893.19		$959.1976	$959.21	$959.15	$959.30