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	$229.42	11.405%	$255.5854	$255.59	$255.60	$255.60
Purchase #2	$195.72	8.203%	$211.7749	$211.77	$211.75	$211.80
Purchase #3	$35.76	9.436%	$39.1343	$39.13	$39.15	$39.10
Purchase #4	$217.62	7.461%	$233.8566	$233.86	$233.85	$233.90
Purchase #5	$161.75	3.298%	$167.0845	$167.08	$167.10	$167.10
Purchase #6	$99.78	4.249%	$104.0197	$104.02	$104.00	$104.00
Purchase #7	$220.80	3.839%	$229.2765	$229.28	$229.30	$229.30
7 purchase totals =	$1,160.85		$1,240.7319	$1,240.73	$1,240.75	$1,240.80