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	$163.80	4.262%	$170.7812	$170.78	$170.80	$170.80
Purchase #2	$88.91	11.103%	$98.7817	$98.78	$98.80	$98.80
Purchase #3	$70.32	4.418%	$73.4267	$73.43	$73.45	$73.40
Purchase #4	$146.69	3.682%	$152.0911	$152.09	$152.10	$152.10
Purchase #5	$129.55	9.528%	$141.8935	$141.89	$141.90	$141.90
Purchase #6	$156.96	10.327%	$173.1693	$173.17	$173.15	$173.20
Purchase #7	$99.27	7.252%	$106.4691	$106.47	$106.45	$106.50
7 purchase totals =	$855.50		$916.6126	$916.61	$916.65	$916.70