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	$130.45	4.372%	$136.1533	$136.15	$136.15	$136.20
Purchase #2	$218.77	5.821%	$231.5046	$231.50	$231.50	$231.50
Purchase #3	$192.77	13.132%	$218.0846	$218.08	$218.10	$218.10
Purchase #4	$146.83	12.776%	$165.589	$165.59	$165.60	$165.60
Purchase #5	$175.45	5.678%	$185.4121	$185.41	$185.40	$185.40
Purchase #6	$239.31	9.482%	$262.0014	$262.00	$262.00	$262.00
Purchase #7	$244.32	4.243%	$254.6865	$254.69	$254.70	$254.70
7 purchase totals =	$1,347.90		$1,453.4315	$1,453.42	$1,453.45	$1,453.50