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	$224.91	6.277%	$239.0276	$239.03	$239.05	$239.00
Purchase #2	$149.82	3.848%	$155.5851	$155.59	$155.60	$155.60
Purchase #3	$153.61	9.536%	$168.2582	$168.26	$168.25	$168.30
Purchase #4	$246.42	3.579%	$255.2394	$255.24	$255.25	$255.20
Purchase #5	$9.76	11.495%	$10.8819	$10.88	$10.90	$10.90
Purchase #6	$211.94	6.436%	$225.5805	$225.58	$225.60	$225.60
Purchase #7	$155.58	10.727%	$172.2691	$172.27	$172.25	$172.30
7 purchase totals =	$1,152.04		$1,226.8418	$1,226.85	$1,226.90	$1,226.90