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	$57.42	8.452%	$62.2731	$62.27	$62.25	$62.30
Purchase #2	$218.95	6.329%	$232.8073	$232.81	$232.80	$232.80
Purchase #3	$222.34	12.477%	$250.0814	$250.08	$250.10	$250.10
Purchase #4	$98.27	13.485%	$111.5217	$111.52	$111.50	$111.50
Purchase #5	$58.67	11.687%	$65.5268	$65.53	$65.55	$65.50
Purchase #6	$33.88	12.278%	$38.0398	$38.04	$38.05	$38.00
Purchase #7	$158.67	9.343%	$173.4945	$173.49	$173.50	$173.50
7 purchase totals =	$848.20		$933.7446	$933.74	$933.75	$933.70