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	$118.68	11.173%	$131.9401	$131.94	$131.95	$131.90
Purchase #2	$71.52	4.607%	$74.8149	$74.81	$74.80	$74.80
Purchase #3	$161.46	13.439%	$183.1586	$183.16	$183.15	$183.20
Purchase #4	$199.31	6.172%	$211.6114	$211.61	$211.60	$211.60
Purchase #5	$29.82	8.244%	$32.2784	$32.28	$32.30	$32.30
Purchase #6	$105.95	5.432%	$111.7052	$111.71	$111.70	$111.70
Purchase #7	$204.54	8.872%	$222.6868	$222.69	$222.70	$222.70
7 purchase totals =	$891.28		$968.1954	$968.20	$968.20	$968.20