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	$59.42	8.518%	$64.4814	$64.48	$64.50	$64.50
Purchase #2	$38.64	11.677%	$43.152	$43.15	$43.15	$43.20
Purchase #3	$127.87	9.385%	$139.8706	$139.87	$139.85	$139.90
Purchase #4	$162.90	10.189%	$179.4979	$179.50	$179.50	$179.50
Purchase #5	$131.27	12.383%	$147.5252	$147.53	$147.55	$147.50
Purchase #6	$17.54	8.128%	$18.9657	$18.97	$18.95	$19.00
Purchase #7	$207.40	3.204%	$214.0451	$214.05	$214.05	$214.00
7 purchase totals =	$745.04		$807.5379	$807.55	$807.55	$807.60