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	$233.90	11.102%	$259.8676	$259.87	$259.85	$259.90
Purchase #2	$83.48	7.186%	$89.4789	$89.48	$89.50	$89.50
Purchase #3	$105.93	11.127%	$117.7168	$117.72	$117.70	$117.70
Purchase #4	$202.64	5.766%	$214.3242	$214.32	$214.30	$214.30
Purchase #5	$101.34	7.252%	$108.6892	$108.69	$108.70	$108.70
Purchase #6	$114.48	7.623%	$123.2068	$123.21	$123.20	$123.20
Purchase #7	$26.39	11.651%	$29.4647	$29.46	$29.45	$29.50
7 purchase totals =	$868.16		$942.7482	$942.75	$942.70	$942.80