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	$86.80	4.162%	$90.4126	$90.41	$90.40	$90.40
Purchase #2	$73.86	5.437%	$77.8758	$77.88	$77.90	$77.90
Purchase #3	$124.76	6.482%	$132.8469	$132.85	$132.85	$132.80
Purchase #4	$11.65	11.151%	$12.9491	$12.95	$12.95	$12.90
Purchase #5	$112.61	13.103%	$127.3653	$127.37	$127.35	$127.40
Purchase #6	$10.77	6.566%	$11.4772	$11.48	$11.50	$11.50
Purchase #7	$220.89	8.540%	$239.754	$239.75	$239.75	$239.80
7 purchase totals =	$641.34		$692.6809	$692.69	$692.70	$692.70