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	$97.34	9.371%	$106.4617	$106.46	$106.45	$106.50
Purchase #2	$162.91	6.478%	$173.4633	$173.46	$173.45	$173.50
Purchase #3	$164.50	7.733%	$177.2208	$177.22	$177.20	$177.20
Purchase #4	$149.60	6.152%	$158.8034	$158.80	$158.80	$158.80
Purchase #5	$245.43	11.557%	$273.7943	$273.79	$273.80	$273.80
Purchase #6	$47.71	13.483%	$54.1427	$54.14	$54.15	$54.10
Purchase #7	$172.37	8.776%	$187.4972	$187.50	$187.50	$187.50
7 purchase totals =	$1,039.86		$1,131.3834	$1,131.37	$1,131.35	$1,131.40