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	$116.75	5.783%	$123.5017	$123.50	$123.50	$123.50
Purchase #2	$31.60	4.259%	$32.9458	$32.95	$32.95	$32.90
Purchase #3	$13.28	11.534%	$14.8117	$14.81	$14.80	$14.80
Purchase #4	$169.48	3.657%	$175.6779	$175.68	$175.70	$175.70
Purchase #5	$110.67	11.492%	$123.3882	$123.39	$123.40	$123.40
Purchase #6	$146.68	5.209%	$154.3206	$154.32	$154.30	$154.30
Purchase #7	$65.28	10.702%	$72.2663	$72.27	$72.25	$72.30
7 purchase totals =	$653.74		$696.9122	$696.92	$696.90	$696.90