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	$215.90	6.679%	$230.32	$230.32	$230.30	$230.30
Purchase #2	$93.27	8.686%	$101.3714	$101.37	$101.35	$101.40
Purchase #3	$200.83	13.169%	$227.2773	$227.28	$227.30	$227.30
Purchase #4	$231.37	7.598%	$248.9495	$248.95	$248.95	$248.90
Purchase #5	$175.88	4.864%	$184.4348	$184.43	$184.45	$184.40
Purchase #6	$99.96	11.206%	$111.1615	$111.16	$111.15	$111.20
Purchase #7	$130.42	6.642%	$139.0825	$139.08	$139.10	$139.10
7 purchase totals =	$1,147.63		$1,242.5970	$1,242.59	$1,242.60	$1,242.60