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	$104.89	11.707%	$117.1695	$117.17	$117.15	$117.20
Purchase #2	$138.97	13.819%	$158.1743	$158.17	$158.15	$158.20
Purchase #3	$56.48	10.448%	$62.381	$62.38	$62.40	$62.40
Purchase #4	$173.39	4.787%	$181.6902	$181.69	$181.70	$181.70
Purchase #5	$177.42	10.637%	$196.2922	$196.29	$196.30	$196.30
Purchase #6	$103.65	7.300%	$111.2165	$111.22	$111.20	$111.20
Purchase #7	$96.90	10.161%	$106.746	$106.75	$106.75	$106.70
7 purchase totals =	$851.70		$933.6697	$933.67	$933.65	$933.70