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	$59.73	4.421%	$62.3707	$62.37	$62.35	$62.40
Purchase #2	$49.28	11.371%	$54.8836	$54.88	$54.90	$54.90
Purchase #3	$120.73	5.351%	$127.1903	$127.19	$127.20	$127.20
Purchase #4	$137.58	4.527%	$143.8082	$143.81	$143.80	$143.80
Purchase #5	$76.83	8.233%	$83.1554	$83.16	$83.15	$83.20
Purchase #6	$171.64	8.643%	$186.4748	$186.47	$186.45	$186.50
Purchase #7	$17.93	10.194%	$19.7578	$19.76	$19.75	$19.80
7 purchase totals =	$633.72		$677.6408	$677.64	$677.60	$677.80