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	$62.93	3.152%	$64.9136	$64.91	$64.90	$64.90
Purchase #2	$53.45	11.590%	$59.6449	$59.64	$59.65	$59.60
Purchase #3	$197.67	5.493%	$208.528	$208.53	$208.55	$208.50
Purchase #4	$161.72	7.283%	$173.4981	$173.50	$173.50	$173.50
Purchase #5	$213.71	9.707%	$234.4548	$234.45	$234.45	$234.50
Purchase #6	$90.79	12.667%	$102.2904	$102.29	$102.30	$102.30
Purchase #7	$241.61	4.280%	$251.9509	$251.95	$251.95	$252.00
7 purchase totals =	$1,021.88		$1,095.2807	$1,095.27	$1,095.30	$1,095.30