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	$164.69	5.157%	$173.1831	$173.18	$173.20	$173.20
Purchase #2	$11.46	8.371%	$12.4193	$12.42	$12.40	$12.40
Purchase #3	$32.51	11.479%	$36.2418	$36.24	$36.25	$36.20
Purchase #4	$38.88	11.792%	$43.4647	$43.46	$43.45	$43.50
Purchase #5	$93.95	9.223%	$102.615	$102.62	$102.60	$102.60
Purchase #6	$92.95	10.739%	$102.9319	$102.93	$102.95	$102.90
Purchase #7	$130.45	10.622%	$144.3064	$144.31	$144.30	$144.30
7 purchase totals =	$564.89		$615.1622	$615.16	$615.15	$615.10