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	$160.27	4.502%	$167.4854	$167.49	$167.50	$167.50
Purchase #2	$49.89	9.194%	$54.4769	$54.48	$54.50	$54.50
Purchase #3	$146.81	3.267%	$151.6063	$151.61	$151.60	$151.60
Purchase #4	$103.31	6.233%	$109.7493	$109.75	$109.75	$109.70
Purchase #5	$147.97	13.422%	$167.8305	$167.83	$167.85	$167.80
Purchase #6	$230.47	8.313%	$249.629	$249.63	$249.65	$249.60
Purchase #7	$117.67	5.106%	$123.6782	$123.68	$123.70	$123.70
7 purchase totals =	$956.39		$1,024.4556	$1,024.47	$1,024.55	$1,024.40