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	$83.40	10.543%	$92.1929	$92.19	$92.20	$92.20
Purchase #2	$41.96	13.808%	$47.7538	$47.75	$47.75	$47.80
Purchase #3	$144.80	4.367%	$151.1234	$151.12	$151.10	$151.10
Purchase #4	$214.93	6.319%	$228.5114	$228.51	$228.50	$228.50
Purchase #5	$223.38	8.164%	$241.6167	$241.62	$241.60	$241.60
Purchase #6	$120.35	10.768%	$133.3093	$133.31	$133.30	$133.30
Purchase #7	$188.78	8.831%	$205.4512	$205.45	$205.45	$205.50
7 purchase totals =	$1,017.60		$1,099.9587	$1,099.95	$1,099.90	$1,100.00