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	$205.92	4.186%	$214.5398	$214.54	$214.55	$214.50
Purchase #2	$70.72	11.495%	$78.8493	$78.85	$78.85	$78.80
Purchase #3	$89.40	10.172%	$98.4938	$98.49	$98.50	$98.50
Purchase #4	$9.96	4.477%	$10.4059	$10.41	$10.40	$10.40
Purchase #5	$60.68	10.869%	$67.2753	$67.28	$67.30	$67.30
Purchase #6	$83.54	8.181%	$90.3744	$90.37	$90.35	$90.40
Purchase #7	$209.89	5.105%	$220.6049	$220.60	$220.60	$220.60
7 purchase totals =	$730.11		$780.5434	$780.54	$780.55	$780.50