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	$150.43	10.777%	$166.6418	$166.64	$166.65	$166.60
Purchase #2	$12.52	8.359%	$13.5665	$13.57	$13.55	$13.60
Purchase #3	$194.25	11.654%	$216.8879	$216.89	$216.90	$216.90
Purchase #4	$208.53	10.402%	$230.2213	$230.22	$230.20	$230.20
Purchase #5	$128.83	10.275%	$142.0673	$142.07	$142.05	$142.10
Purchase #6	$132.56	6.385%	$141.024	$141.02	$141.00	$141.00
Purchase #7	$20.31	12.820%	$22.9137	$22.91	$22.90	$22.90
7 purchase totals =	$847.43		$933.3225	$933.32	$933.25	$933.30