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	$242.81	8.325%	$263.0239	$263.02	$263.00	$263.00
Purchase #2	$61.48	7.362%	$66.0062	$66.01	$66.00	$66.00
Purchase #3	$233.73	11.530%	$260.6791	$260.68	$260.70	$260.70
Purchase #4	$168.39	3.103%	$173.6151	$173.62	$173.60	$173.60
Purchase #5	$114.88	5.195%	$120.848	$120.85	$120.85	$120.80
Purchase #6	$112.26	13.560%	$127.4825	$127.48	$127.50	$127.50
Purchase #7	$101.53	9.840%	$111.5206	$111.52	$111.50	$111.50
7 purchase totals =	$1,035.08		$1,123.1754	$1,123.18	$1,123.15	$1,123.10