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	$97.77	10.818%	$108.3468	$108.35	$108.35	$108.30
Purchase #2	$71.75	8.500%	$77.8488	$77.85	$77.85	$77.80
Purchase #3	$154.81	11.684%	$172.898	$172.90	$172.90	$172.90
Purchase #4	$51.82	5.420%	$54.6286	$54.63	$54.65	$54.60
Purchase #5	$64.81	12.370%	$72.827	$72.83	$72.85	$72.80
Purchase #6	$57.97	11.172%	$64.4464	$64.45	$64.45	$64.40
Purchase #7	$195.78	13.143%	$221.5114	$221.51	$221.50	$221.50
7 purchase totals =	$694.71		$772.5070	$772.52	$772.55	$772.30