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	$181.64	6.304%	$193.0906	$193.09	$193.10	$193.10
Purchase #2	$114.56	11.538%	$127.7779	$127.78	$127.80	$127.80
Purchase #3	$104.49	3.831%	$108.493	$108.49	$108.50	$108.50
Purchase #4	$172.28	4.462%	$179.9671	$179.97	$179.95	$180.00
Purchase #5	$245.64	3.759%	$254.8736	$254.87	$254.85	$254.90
Purchase #6	$146.72	10.205%	$161.6928	$161.69	$161.70	$161.70
Purchase #7	$163.34	4.169%	$170.1496	$170.15	$170.15	$170.10
7 purchase totals =	$1,128.67		$1,196.0446	$1,196.04	$1,196.05	$1,196.10