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	$49.25	8.798%	$53.583	$53.58	$53.60	$53.60
Purchase #2	$231.57	10.413%	$255.6834	$255.68	$255.70	$255.70
Purchase #3	$183.31	12.674%	$206.5427	$206.54	$206.55	$206.50
Purchase #4	$240.78	7.491%	$258.8168	$258.82	$258.80	$258.80
Purchase #5	$13.74	11.422%	$15.3094	$15.31	$15.30	$15.30
Purchase #6	$248.61	12.519%	$279.7335	$279.73	$279.75	$279.70
Purchase #7	$55.31	11.191%	$61.4997	$61.50	$61.50	$61.50
7 purchase totals =	$1,022.57		$1,131.1685	$1,131.16	$1,131.20	$1,131.10