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	$98.55	7.190%	$105.6357	$105.64	$105.65	$105.60
Purchase #2	$214.52	13.826%	$244.1795	$244.18	$244.20	$244.20
Purchase #3	$202.32	4.640%	$211.7076	$211.71	$211.70	$211.70
Purchase #4	$181.44	5.168%	$190.8168	$190.82	$190.80	$190.80
Purchase #5	$137.33	11.657%	$153.3386	$153.34	$153.35	$153.30
Purchase #6	$35.74	5.653%	$37.7604	$37.76	$37.75	$37.80
Purchase #7	$172.50	10.403%	$190.4452	$190.45	$190.45	$190.40
7 purchase totals =	$1,042.40		$1,133.8838	$1,133.90	$1,133.90	$1,133.80