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	$13.66	8.567%	$14.8303	$14.83	$14.85	$14.80
Purchase #2	$224.94	6.687%	$239.9817	$239.98	$240.00	$240.00
Purchase #3	$172.35	4.255%	$179.6835	$179.68	$179.70	$179.70
Purchase #4	$41.61	10.310%	$45.9	$45.90	$45.90	$45.90
Purchase #5	$176.73	6.597%	$188.3889	$188.39	$188.40	$188.40
Purchase #6	$151.27	5.375%	$159.4008	$159.40	$159.40	$159.40
Purchase #7	$95.56	5.128%	$100.4603	$100.46	$100.45	$100.50
7 purchase totals =	$876.12		$928.6455	$928.64	$928.70	$928.70