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	$160.30	4.600%	$167.6738	$167.67	$167.65	$167.70
Purchase #2	$188.78	13.580%	$214.4163	$214.42	$214.40	$214.40
Purchase #3	$127.45	5.195%	$134.071	$134.07	$134.05	$134.10
Purchase #4	$216.28	9.443%	$236.7033	$236.70	$236.70	$236.70
Purchase #5	$27.38	6.371%	$29.1244	$29.12	$29.10	$29.10
Purchase #6	$243.85	7.508%	$262.1583	$262.16	$262.15	$262.20
Purchase #7	$52.73	12.602%	$59.375	$59.38	$59.40	$59.40
7 purchase totals =	$1,016.77		$1,103.5221	$1,103.52	$1,103.45	$1,103.60