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	$70.29	8.622%	$76.3504	$76.35	$76.35	$76.40
Purchase #2	$98.39	4.240%	$102.5617	$102.56	$102.55	$102.60
Purchase #3	$124.28	5.160%	$130.6928	$130.69	$130.70	$130.70
Purchase #4	$51.85	10.648%	$57.371	$57.37	$57.35	$57.40
Purchase #5	$236.51	7.604%	$254.4942	$254.49	$254.50	$254.50
Purchase #6	$70.75	10.569%	$78.2276	$78.23	$78.25	$78.20
Purchase #7	$247.67	13.794%	$281.8336	$281.83	$281.85	$281.80
7 purchase totals =	$899.74		$981.5313	$981.52	$981.55	$981.60