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	$246.25	5.108%	$258.8285	$258.83	$258.85	$258.80
Purchase #2	$92.30	5.385%	$97.2704	$97.27	$97.25	$97.30
Purchase #3	$103.89	8.492%	$112.7123	$112.71	$112.70	$112.70
Purchase #4	$98.77	12.463%	$111.0797	$111.08	$111.10	$111.10
Purchase #5	$60.40	10.295%	$66.6182	$66.62	$66.60	$66.60
Purchase #6	$226.66	6.854%	$242.1953	$242.20	$242.20	$242.20
Purchase #7	$52.90	11.792%	$59.138	$59.14	$59.15	$59.10
7 purchase totals =	$881.17		$947.8424	$947.85	$947.85	$947.80