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	$183.60	9.230%	$200.5463	$200.55	$200.55	$200.50
Purchase #2	$139.49	4.716%	$146.0683	$146.07	$146.05	$146.10
Purchase #3	$214.52	13.868%	$244.2696	$244.27	$244.25	$244.30
Purchase #4	$187.72	13.203%	$212.5047	$212.50	$212.50	$212.50
Purchase #5	$250.34	10.874%	$277.562	$277.56	$277.55	$277.60
Purchase #6	$217.30	12.712%	$244.9232	$244.92	$244.90	$244.90
Purchase #7	$78.28	5.219%	$82.3654	$82.37	$82.35	$82.40
7 purchase totals =	$1,271.25		$1,408.2395	$1,408.24	$1,408.15	$1,408.30