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	$229.45	11.628%	$256.1304	$256.13	$256.15	$256.10
Purchase #2	$160.84	10.734%	$178.1046	$178.10	$178.10	$178.10
Purchase #3	$248.36	3.347%	$256.6726	$256.67	$256.65	$256.70
Purchase #4	$151.27	4.713%	$158.3994	$158.40	$158.40	$158.40
Purchase #5	$51.45	13.393%	$58.3407	$58.34	$58.35	$58.30
Purchase #6	$99.48	12.379%	$111.7946	$111.79	$111.80	$111.80
Purchase #7	$223.76	5.262%	$235.5343	$235.53	$235.55	$235.50
7 purchase totals =	$1,164.61		$1,254.9766	$1,254.96	$1,255.00	$1,254.90