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	$87.95	8.848%	$95.7318	$95.73	$95.75	$95.70
Purchase #2	$120.54	11.733%	$134.683	$134.68	$134.70	$134.70
Purchase #3	$156.77	5.873%	$165.9771	$165.98	$166.00	$166.00
Purchase #4	$104.54	6.717%	$111.562	$111.56	$111.55	$111.60
Purchase #5	$60.37	7.201%	$64.7172	$64.72	$64.70	$64.70
Purchase #6	$118.87	11.769%	$132.8598	$132.86	$132.85	$132.90
Purchase #7	$240.32	4.388%	$250.8652	$250.87	$250.85	$250.90
7 purchase totals =	$889.36		$956.3961	$956.40	$956.40	$956.50