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	$230.61	10.324%	$254.4182	$254.42	$254.40	$254.40
Purchase #2	$40.32	8.792%	$43.8649	$43.86	$43.85	$43.90
Purchase #3	$224.87	4.820%	$235.7087	$235.71	$235.70	$235.70
Purchase #4	$165.89	9.268%	$181.2647	$181.26	$181.25	$181.30
Purchase #5	$92.87	7.521%	$99.8548	$99.85	$99.85	$99.90
Purchase #6	$225.35	11.352%	$250.9317	$250.93	$250.95	$250.90
Purchase #7	$143.66	8.710%	$156.1728	$156.17	$156.15	$156.20
7 purchase totals =	$1,123.57		$1,222.2158	$1,222.20	$1,222.15	$1,222.30