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	$247.56	9.640%	$271.4248	$271.42	$271.40	$271.40
Purchase #2	$92.25	9.244%	$100.7776	$100.78	$100.80	$100.80
Purchase #3	$226.67	12.620%	$255.2758	$255.28	$255.30	$255.30
Purchase #4	$62.70	5.420%	$66.0983	$66.10	$66.10	$66.10
Purchase #5	$30.69	13.537%	$34.8445	$34.84	$34.85	$34.80
Purchase #6	$62.64	3.523%	$64.8468	$64.85	$64.85	$64.80
Purchase #7	$243.46	7.860%	$262.596	$262.60	$262.60	$262.60
7 purchase totals =	$965.97		$1,055.8638	$1,055.87	$1,055.90	$1,055.80