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	$176.43	6.846%	$188.5084	$188.51	$188.50	$188.50
Purchase #2	$17.34	12.268%	$19.4673	$19.47	$19.45	$19.50
Purchase #3	$44.85	4.534%	$46.8835	$46.88	$46.90	$46.90
Purchase #4	$118.99	7.189%	$127.5442	$127.54	$127.55	$127.50
Purchase #5	$29.35	6.520%	$31.2636	$31.26	$31.25	$31.30
Purchase #6	$94.50	13.793%	$107.5344	$107.53	$107.55	$107.50
Purchase #7	$56.82	5.583%	$59.9923	$59.99	$60.00	$60.00
7 purchase totals =	$538.28		$581.1937	$581.18	$581.20	$581.20