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	$204.43	12.858%	$230.7156	$230.72	$230.70	$230.70
Purchase #2	$44.92	3.263%	$46.3857	$46.39	$46.40	$46.40
Purchase #3	$174.83	12.644%	$196.9355	$196.94	$196.95	$196.90
Purchase #4	$219.52	10.526%	$242.6267	$242.63	$242.65	$242.60
Purchase #5	$100.71	4.710%	$105.4534	$105.45	$105.45	$105.50
Purchase #6	$40.93	8.718%	$44.4983	$44.50	$44.50	$44.50
Purchase #7	$106.50	10.812%	$118.0148	$118.01	$118.00	$118.00
7 purchase totals =	$891.84		$984.6300	$984.64	$984.65	$984.60