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	$54.57	13.232%	$61.7907	$61.79	$61.80	$61.80
Purchase #2	$132.72	13.721%	$150.9305	$150.93	$150.95	$150.90
Purchase #3	$244.27	4.520%	$255.311	$255.31	$255.30	$255.30
Purchase #4	$200.43	10.671%	$221.8179	$221.82	$221.80	$221.80
Purchase #5	$239.49	5.466%	$252.5805	$252.58	$252.60	$252.60
Purchase #6	$208.38	7.481%	$223.9689	$223.97	$223.95	$224.00
Purchase #7	$227.37	3.219%	$234.689	$234.69	$234.70	$234.70
7 purchase totals =	$1,307.23		$1,401.0885	$1,401.09	$1,401.10	$1,401.10