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	$185.82	10.632%	$205.5764	$205.58	$205.60	$205.60
Purchase #2	$34.43	5.527%	$36.3329	$36.33	$36.35	$36.30
Purchase #3	$141.27	13.414%	$160.22	$160.22	$160.20	$160.20
Purchase #4	$122.27	12.685%	$137.7799	$137.78	$137.80	$137.80
Purchase #5	$236.72	12.411%	$266.0993	$266.10	$266.10	$266.10
Purchase #6	$188.66	3.434%	$195.1386	$195.14	$195.15	$195.10
Purchase #7	$72.42	8.534%	$78.6003	$78.60	$78.60	$78.60
7 purchase totals =	$981.59		$1,079.7474	$1,079.75	$1,079.80	$1,079.70