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	$31.51	5.248%	$33.1636	$33.16	$33.15	$33.20
Purchase #2	$120.53	5.492%	$127.1495	$127.15	$127.15	$127.10
Purchase #3	$206.45	6.475%	$219.8176	$219.82	$219.80	$219.80
Purchase #4	$65.66	13.801%	$74.7217	$74.72	$74.70	$74.70
Purchase #5	$112.43	3.183%	$116.0086	$116.01	$116.00	$116.00
Purchase #6	$19.76	11.706%	$22.0731	$22.07	$22.05	$22.10
Purchase #7	$157.38	10.294%	$173.5807	$173.58	$173.60	$173.60
7 purchase totals =	$713.72		$766.5148	$766.51	$766.45	$766.50