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	$129.64	11.136%	$144.0767	$144.08	$144.10	$144.10
Purchase #2	$22.40	4.412%	$23.3883	$23.39	$23.40	$23.40
Purchase #3	$127.43	3.186%	$131.4899	$131.49	$131.50	$131.50
Purchase #4	$231.97	12.332%	$260.5765	$260.58	$260.60	$260.60
Purchase #5	$39.61	4.607%	$41.4348	$41.43	$41.45	$41.40
Purchase #6	$65.90	10.175%	$72.6053	$72.61	$72.60	$72.60
Purchase #7	$169.73	5.359%	$178.8258	$178.83	$178.85	$178.80
7 purchase totals =	$786.68		$852.3973	$852.41	$852.50	$852.40