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	$99.59	11.544%	$111.0867	$111.09	$111.10	$111.10
Purchase #2	$217.64	5.256%	$229.0792	$229.08	$229.10	$229.10
Purchase #3	$158.67	10.205%	$174.8623	$174.86	$174.85	$174.90
Purchase #4	$114.74	7.710%	$123.5865	$123.59	$123.60	$123.60
Purchase #5	$207.37	11.230%	$230.6577	$230.66	$230.65	$230.70
Purchase #6	$126.86	4.665%	$132.778	$132.78	$132.80	$132.80
Purchase #7	$43.34	9.442%	$47.4322	$47.43	$47.45	$47.40
7 purchase totals =	$968.21		$1,049.4826	$1,049.49	$1,049.55	$1,049.60