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	$242.82	8.147%	$262.6025	$262.60	$262.60	$262.60
Purchase #2	$41.85	8.774%	$45.5219	$45.52	$45.50	$45.50
Purchase #3	$54.91	10.505%	$60.6783	$60.68	$60.70	$60.70
Purchase #4	$102.26	8.630%	$111.085	$111.09	$111.10	$111.10
Purchase #5	$217.34	5.737%	$229.8088	$229.81	$229.80	$229.80
Purchase #6	$14.97	12.530%	$16.8457	$16.85	$16.85	$16.80
Purchase #7	$89.31	11.638%	$99.7039	$99.70	$99.70	$99.70
7 purchase totals =	$763.46		$826.2461	$826.25	$826.25	$826.20