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	$103.67	7.571%	$111.5189	$111.52	$111.50	$111.50
Purchase #2	$43.70	3.456%	$45.2103	$45.21	$45.20	$45.20
Purchase #3	$223.89	10.273%	$246.8902	$246.89	$246.90	$246.90
Purchase #4	$129.25	7.793%	$139.3225	$139.32	$139.30	$139.30
Purchase #5	$58.32	12.553%	$65.6409	$65.64	$65.65	$65.60
Purchase #6	$30.94	12.252%	$34.7308	$34.73	$34.75	$34.70
Purchase #7	$177.37	3.638%	$183.8227	$183.82	$183.80	$183.80
7 purchase totals =	$767.14		$827.1363	$827.13	$827.10	$827.00