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	$127.47	13.205%	$144.3024	$144.30	$144.30	$144.30
Purchase #2	$114.30	4.389%	$119.3166	$119.32	$119.30	$119.30
Purchase #3	$214.45	8.136%	$231.8977	$231.90	$231.90	$231.90
Purchase #4	$14.86	11.247%	$16.5313	$16.53	$16.55	$16.50
Purchase #5	$166.71	4.624%	$174.4187	$174.42	$174.40	$174.40
Purchase #6	$196.56	13.157%	$222.4214	$222.42	$222.40	$222.40
Purchase #7	$147.30	4.778%	$154.338	$154.34	$154.35	$154.30
7 purchase totals =	$981.65		$1,063.2261	$1,063.23	$1,063.20	$1,063.10