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	$11.65	3.575%	$12.0665	$12.07	$12.05	$12.10
Purchase #2	$173.25	13.526%	$196.6838	$196.68	$196.70	$196.70
Purchase #3	$142.54	8.644%	$154.8612	$154.86	$154.85	$154.90
Purchase #4	$65.52	3.626%	$67.8958	$67.90	$67.90	$67.90
Purchase #5	$48.45	8.160%	$52.4035	$52.40	$52.40	$52.40
Purchase #6	$42.95	8.216%	$46.4788	$46.48	$46.50	$46.50
Purchase #7	$246.65	7.855%	$266.0244	$266.02	$266.00	$266.00
7 purchase totals =	$731.01		$796.4140	$796.41	$796.40	$796.50