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	$221.76	4.350%	$231.4066	$231.41	$231.40	$231.40
Purchase #2	$6.58	5.184%	$6.9211	$6.92	$6.90	$6.90
Purchase #3	$48.96	8.301%	$53.0242	$53.02	$53.00	$53.00
Purchase #4	$78.31	6.144%	$83.1214	$83.12	$83.10	$83.10
Purchase #5	$108.39	9.118%	$118.273	$118.27	$118.25	$118.30
Purchase #6	$69.76	13.142%	$78.9279	$78.93	$78.95	$78.90
Purchase #7	$105.77	6.204%	$112.332	$112.33	$112.35	$112.30
7 purchase totals =	$639.53		$684.0062	$684.00	$683.95	$683.90