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	$205.39	4.281%	$214.1827	$214.18	$214.20	$214.20
Purchase #2	$136.59	8.685%	$148.4528	$148.45	$148.45	$148.50
Purchase #3	$117.61	5.357%	$123.9104	$123.91	$123.90	$123.90
Purchase #4	$154.53	7.124%	$165.5387	$165.54	$165.55	$165.50
Purchase #5	$26.58	10.527%	$29.3781	$29.38	$29.40	$29.40
Purchase #6	$186.37	6.321%	$198.1504	$198.15	$198.15	$198.20
Purchase #7	$234.43	5.162%	$246.5313	$246.53	$246.55	$246.50
7 purchase totals =	$1,061.50		$1,126.1444	$1,126.14	$1,126.20	$1,126.20