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	$117.39	6.826%	$125.403	$125.40	$125.40	$125.40
Purchase #2	$109.45	7.388%	$117.5362	$117.54	$117.55	$117.50
Purchase #3	$59.72	3.538%	$61.8329	$61.83	$61.85	$61.80
Purchase #4	$78.78	11.408%	$87.7672	$87.77	$87.75	$87.80
Purchase #5	$44.26	7.732%	$47.6822	$47.68	$47.70	$47.70
Purchase #6	$68.73	6.182%	$72.9789	$72.98	$73.00	$73.00
Purchase #7	$64.82	11.553%	$72.3087	$72.31	$72.30	$72.30
7 purchase totals =	$543.15		$585.5091	$585.51	$585.55	$585.50