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	$103.37	7.575%	$111.2003	$111.20	$111.20	$111.20
Purchase #2	$144.84	9.305%	$158.3174	$158.32	$158.30	$158.30
Purchase #3	$183.64	8.528%	$199.3008	$199.30	$199.30	$199.30
Purchase #4	$130.37	12.184%	$146.2543	$146.25	$146.25	$146.30
Purchase #5	$54.98	8.525%	$59.667	$59.67	$59.65	$59.70
Purchase #6	$29.94	5.289%	$31.5235	$31.52	$31.50	$31.50
Purchase #7	$141.33	3.108%	$145.7225	$145.72	$145.70	$145.70
7 purchase totals =	$788.47		$851.9858	$851.98	$851.90	$852.00