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	$162.78	5.840%	$172.2864	$172.29	$172.30	$172.30
Purchase #2	$96.43	10.651%	$106.7008	$106.70	$106.70	$106.70
Purchase #3	$56.38	4.108%	$58.6961	$58.70	$58.70	$58.70
Purchase #4	$133.82	6.756%	$142.8609	$142.86	$142.85	$142.90
Purchase #5	$90.61	13.669%	$102.9955	$103.00	$103.00	$103.00
Purchase #6	$42.51	9.866%	$46.704	$46.70	$46.70	$46.70
Purchase #7	$131.55	8.162%	$142.2871	$142.29	$142.30	$142.30
7 purchase totals =	$714.08		$772.5308	$772.54	$772.55	$772.60