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	$82.46	12.365%	$92.6562	$92.66	$92.65	$92.70
Purchase #2	$175.70	6.680%	$187.4368	$187.44	$187.45	$187.40
Purchase #3	$230.62	3.583%	$238.8831	$238.88	$238.90	$238.90
Purchase #4	$10.63	13.208%	$12.034	$12.03	$12.05	$12.00
Purchase #5	$186.94	9.810%	$205.2788	$205.28	$205.30	$205.30
Purchase #6	$137.70	5.152%	$144.7943	$144.79	$144.80	$144.80
Purchase #7	$29.42	13.342%	$33.3452	$33.35	$33.35	$33.30
7 purchase totals =	$853.47		$914.4284	$914.43	$914.50	$914.40