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	$168.42	6.637%	$179.598	$179.60	$179.60	$179.60
Purchase #2	$95.70	7.698%	$103.067	$103.07	$103.05	$103.10
Purchase #3	$226.97	12.680%	$255.7498	$255.75	$255.75	$255.70
Purchase #4	$204.78	4.675%	$214.3535	$214.35	$214.35	$214.40
Purchase #5	$215.56	8.862%	$234.6629	$234.66	$234.65	$234.70
Purchase #6	$82.57	8.548%	$89.6281	$89.63	$89.65	$89.60
Purchase #7	$61.68	8.317%	$66.8099	$66.81	$66.80	$66.80
7 purchase totals =	$1,055.68		$1,143.8692	$1,143.87	$1,143.85	$1,143.90