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	$139.91	9.749%	$153.5498	$153.55	$153.55	$153.50
Purchase #2	$65.27	13.118%	$73.8321	$73.83	$73.85	$73.80
Purchase #3	$118.76	5.112%	$124.831	$124.83	$124.85	$124.80
Purchase #4	$125.91	13.813%	$143.3019	$143.30	$143.30	$143.30
Purchase #5	$148.60	4.201%	$154.8427	$154.84	$154.85	$154.80
Purchase #6	$94.68	5.621%	$100.002	$100.00	$100.00	$100.00
Purchase #7	$111.75	8.149%	$120.8565	$120.86	$120.85	$120.90
7 purchase totals =	$804.88		$871.2160	$871.21	$871.25	$871.10