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	$160.64	3.752%	$166.6672	$166.67	$166.65	$166.70
Purchase #2	$149.87	10.577%	$165.7217	$165.72	$165.70	$165.70
Purchase #3	$95.84	5.120%	$100.747	$100.75	$100.75	$100.70
Purchase #4	$138.29	10.340%	$152.5892	$152.59	$152.60	$152.60
Purchase #5	$239.56	11.643%	$267.452	$267.45	$267.45	$267.50
Purchase #6	$127.25	11.589%	$141.997	$142.00	$142.00	$142.00
Purchase #7	$224.69	4.197%	$234.1202	$234.12	$234.10	$234.10
7 purchase totals =	$1,136.14		$1,229.2943	$1,229.30	$1,229.25	$1,229.30