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	$63.65	13.786%	$72.4248	$72.42	$72.40	$72.40
Purchase #2	$60.59	9.753%	$66.4993	$66.50	$66.50	$66.50
Purchase #3	$14.79	12.839%	$16.6889	$16.69	$16.70	$16.70
Purchase #4	$166.41	13.869%	$189.4894	$189.49	$189.50	$189.50
Purchase #5	$142.38	6.116%	$151.088	$151.09	$151.10	$151.10
Purchase #6	$129.53	5.638%	$136.8329	$136.83	$136.85	$136.80
Purchase #7	$89.78	7.513%	$96.5252	$96.53	$96.55	$96.50
7 purchase totals =	$667.13		$729.5485	$729.55	$729.60	$729.50