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	$59.27	3.715%	$61.4719	$61.47	$61.45	$61.50
Purchase #2	$133.29	4.667%	$139.5106	$139.51	$139.50	$139.50
Purchase #3	$133.99	13.277%	$151.7799	$151.78	$151.80	$151.80
Purchase #4	$63.89	7.452%	$68.6511	$68.65	$68.65	$68.70
Purchase #5	$56.39	10.449%	$62.2822	$62.28	$62.30	$62.30
Purchase #6	$227.79	13.858%	$259.3571	$259.36	$259.35	$259.40
Purchase #7	$244.85	5.810%	$259.0758	$259.08	$259.10	$259.10
7 purchase totals =	$919.47		$1,002.1286	$1,002.13	$1,002.15	$1,002.30