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	$50.84	10.213%	$56.0323	$56.03	$56.05	$56.00
Purchase #2	$172.31	11.143%	$191.5105	$191.51	$191.50	$191.50
Purchase #3	$225.77	13.388%	$255.9961	$256.00	$256.00	$256.00
Purchase #4	$39.39	10.612%	$43.5701	$43.57	$43.55	$43.60
Purchase #5	$71.78	13.157%	$81.2241	$81.22	$81.20	$81.20
Purchase #6	$85.93	11.135%	$95.4983	$95.50	$95.50	$95.50
Purchase #7	$114.69	11.215%	$127.5525	$127.55	$127.55	$127.60
7 purchase totals =	$760.71		$851.3839	$851.38	$851.35	$851.40