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	$7.90	13.337%	$8.9536	$8.95	$8.95	$9.00
Purchase #2	$135.87	5.457%	$143.2844	$143.28	$143.30	$143.30
Purchase #3	$214.30	5.234%	$225.5165	$225.52	$225.50	$225.50
Purchase #4	$233.65	10.718%	$258.6926	$258.69	$258.70	$258.70
Purchase #5	$177.83	4.253%	$185.3931	$185.39	$185.40	$185.40
Purchase #6	$91.75	4.235%	$95.6356	$95.64	$95.65	$95.60
Purchase #7	$86.25	11.714%	$96.3533	$96.35	$96.35	$96.40
7 purchase totals =	$947.55		$1,013.8291	$1,013.82	$1,013.85	$1,013.90