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	$204.65	6.238%	$217.4161	$217.42	$217.40	$217.40
Purchase #2	$179.42	4.826%	$188.0788	$188.08	$188.10	$188.10
Purchase #3	$173.31	7.136%	$185.6774	$185.68	$185.70	$185.70
Purchase #4	$106.33	5.146%	$111.8017	$111.80	$111.80	$111.80
Purchase #5	$46.90	13.536%	$53.2484	$53.25	$53.25	$53.20
Purchase #6	$103.80	3.841%	$107.787	$107.79	$107.80	$107.80
Purchase #7	$91.40	13.843%	$104.0525	$104.05	$104.05	$104.10
7 purchase totals =	$905.81		$968.0619	$968.07	$968.10	$968.10