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	$82.61	7.548%	$88.8454	$88.85	$88.85	$88.80
Purchase #2	$143.82	10.181%	$158.4623	$158.46	$158.45	$158.50
Purchase #3	$143.35	11.766%	$160.2166	$160.22	$160.20	$160.20
Purchase #4	$108.66	5.544%	$114.6841	$114.68	$114.70	$114.70
Purchase #5	$40.85	12.498%	$45.9554	$45.96	$45.95	$46.00
Purchase #6	$100.70	7.147%	$107.897	$107.90	$107.90	$107.90
Purchase #7	$115.31	9.621%	$126.404	$126.40	$126.40	$126.40
7 purchase totals =	$735.30		$802.4648	$802.47	$802.45	$802.50