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	$40.41	12.785%	$45.5764	$45.58	$45.60	$45.60
Purchase #2	$146.98	6.513%	$156.5528	$156.55	$156.55	$156.60
Purchase #3	$144.96	9.643%	$158.9385	$158.94	$158.95	$158.90
Purchase #4	$214.98	10.672%	$237.9227	$237.92	$237.90	$237.90
Purchase #5	$248.39	9.252%	$271.371	$271.37	$271.35	$271.40
Purchase #6	$28.50	9.719%	$31.2699	$31.27	$31.25	$31.30
Purchase #7	$166.87	3.575%	$172.8356	$172.84	$172.85	$172.80
7 purchase totals =	$991.09		$1,074.4669	$1,074.47	$1,074.45	$1,074.50