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	$92.47	10.208%	$101.9093	$101.91	$101.90	$101.90
Purchase #2	$200.36	11.105%	$222.61	$222.61	$222.60	$222.60
Purchase #3	$100.69	5.592%	$106.3206	$106.32	$106.30	$106.30
Purchase #4	$214.55	7.304%	$230.2207	$230.22	$230.20	$230.20
Purchase #5	$243.88	12.551%	$274.4894	$274.49	$274.50	$274.50
Purchase #6	$21.32	10.345%	$23.5256	$23.53	$23.55	$23.50
Purchase #7	$81.60	10.410%	$90.0946	$90.09	$90.10	$90.10
7 purchase totals =	$954.87		$1,049.1702	$1,049.17	$1,049.15	$1,049.10