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	$200.92	9.236%	$219.477	$219.48	$219.50	$219.50
Purchase #2	$202.73	11.279%	$225.5959	$225.60	$225.60	$225.60
Purchase #3	$49.86	9.247%	$54.4706	$54.47	$54.45	$54.50
Purchase #4	$45.55	11.773%	$50.9126	$50.91	$50.90	$50.90
Purchase #5	$51.73	5.768%	$54.7138	$54.71	$54.70	$54.70
Purchase #6	$62.44	6.584%	$66.551	$66.55	$66.55	$66.60
Purchase #7	$105.69	5.408%	$111.4057	$111.41	$111.40	$111.40
7 purchase totals =	$718.92		$783.1266	$783.13	$783.10	$783.20