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	$113.51	4.308%	$118.4	$118.40	$118.40	$118.40
Purchase #2	$16.83	13.727%	$19.1403	$19.14	$19.15	$19.10
Purchase #3	$112.52	12.586%	$126.6818	$126.68	$126.70	$126.70
Purchase #4	$97.25	8.328%	$105.349	$105.35	$105.35	$105.30
Purchase #5	$166.62	10.392%	$183.9352	$183.94	$183.95	$183.90
Purchase #6	$167.84	13.667%	$190.7787	$190.78	$190.80	$190.80
Purchase #7	$98.83	7.139%	$105.8855	$105.89	$105.90	$105.90
7 purchase totals =	$773.40		$850.1705	$850.18	$850.25	$850.10