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	$49.99	6.209%	$53.0939	$53.09	$53.10	$53.10
Purchase #2	$246.52	6.583%	$262.7484	$262.75	$262.75	$262.70
Purchase #3	$152.52	4.212%	$158.9441	$158.94	$158.95	$158.90
Purchase #4	$102.43	8.861%	$111.5063	$111.51	$111.50	$111.50
Purchase #5	$52.47	7.447%	$56.3774	$56.38	$56.40	$56.40
Purchase #6	$17.48	10.472%	$19.3105	$19.31	$19.30	$19.30
Purchase #7	$200.88	7.154%	$215.251	$215.25	$215.25	$215.30
7 purchase totals =	$822.29		$877.2316	$877.23	$877.25	$877.20