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	$176.42	3.142%	$181.9631	$181.96	$181.95	$182.00
Purchase #2	$51.86	5.168%	$54.5401	$54.54	$54.55	$54.50
Purchase #3	$102.94	3.237%	$106.2722	$106.27	$106.25	$106.30
Purchase #4	$247.96	3.245%	$256.0063	$256.01	$256.00	$256.00
Purchase #5	$18.32	12.382%	$20.5884	$20.59	$20.60	$20.60
Purchase #6	$61.61	6.291%	$65.4859	$65.49	$65.50	$65.50
Purchase #7	$143.32	4.636%	$149.9643	$149.96	$149.95	$150.00
7 purchase totals =	$802.43		$834.8203	$834.82	$834.80	$834.90