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	$126.53	4.651%	$132.4149	$132.41	$132.40	$132.40
Purchase #2	$48.38	10.391%	$53.4072	$53.41	$53.40	$53.40
Purchase #3	$142.70	3.832%	$148.1683	$148.17	$148.15	$148.20
Purchase #4	$228.49	5.433%	$240.9039	$240.90	$240.90	$240.90
Purchase #5	$100.31	11.519%	$111.8647	$111.86	$111.85	$111.90
Purchase #6	$127.52	8.831%	$138.7813	$138.78	$138.80	$138.80
Purchase #7	$165.78	7.245%	$177.7908	$177.79	$177.80	$177.80
7 purchase totals =	$939.71		$1,003.3311	$1,003.32	$1,003.30	$1,003.40