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	$213.84	4.491%	$223.4436	$223.44	$223.45	$223.40
Purchase #2	$139.41	13.149%	$157.741	$157.74	$157.75	$157.70
Purchase #3	$48.58	3.490%	$50.2754	$50.28	$50.30	$50.30
Purchase #4	$64.37	3.496%	$66.6204	$66.62	$66.60	$66.60
Purchase #5	$137.70	9.315%	$150.5268	$150.53	$150.55	$150.50
Purchase #6	$120.29	6.284%	$127.849	$127.85	$127.85	$127.80
Purchase #7	$148.78	5.434%	$156.8647	$156.86	$156.85	$156.90
7 purchase totals =	$872.97		$933.3209	$933.32	$933.35	$933.20