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	$183.72	8.599%	$199.5181	$199.52	$199.50	$199.50
Purchase #2	$128.67	10.166%	$141.7506	$141.75	$141.75	$141.80
Purchase #3	$100.39	11.301%	$111.7351	$111.74	$111.75	$111.70
Purchase #4	$200.85	12.841%	$226.6411	$226.64	$226.65	$226.60
Purchase #5	$82.26	4.369%	$85.8539	$85.85	$85.85	$85.90
Purchase #6	$12.48	5.642%	$13.1841	$13.18	$13.20	$13.20
Purchase #7	$94.74	5.811%	$100.2453	$100.25	$100.25	$100.20
7 purchase totals =	$803.11		$878.9282	$878.93	$878.95	$878.90