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	$20.29	11.176%	$22.5576	$22.56	$22.55	$22.60
Purchase #2	$214.83	8.662%	$233.4386	$233.44	$233.45	$233.40
Purchase #3	$67.85	4.747%	$71.0708	$71.07	$71.05	$71.10
Purchase #4	$240.46	4.262%	$250.7084	$250.71	$250.70	$250.70
Purchase #5	$159.32	5.500%	$168.0826	$168.08	$168.10	$168.10
Purchase #6	$171.80	10.855%	$190.4489	$190.45	$190.45	$190.40
Purchase #7	$92.50	10.823%	$102.5113	$102.51	$102.50	$102.50
7 purchase totals =	$967.05		$1,038.8182	$1,038.82	$1,038.80	$1,038.80