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	$49.72	7.733%	$53.5648	$53.56	$53.55	$53.60
Purchase #2	$98.74	3.448%	$102.1446	$102.14	$102.15	$102.10
Purchase #3	$173.31	4.243%	$180.6635	$180.66	$180.65	$180.70
Purchase #4	$114.96	10.710%	$127.2722	$127.27	$127.25	$127.30
Purchase #5	$139.81	7.427%	$150.1937	$150.19	$150.20	$150.20
Purchase #6	$63.45	4.800%	$66.4956	$66.50	$66.50	$66.50
Purchase #7	$227.26	3.196%	$234.5232	$234.52	$234.50	$234.50
7 purchase totals =	$867.25		$914.8576	$914.84	$914.80	$914.90