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	$223.77	3.201%	$230.9329	$230.93	$230.95	$230.90
Purchase #2	$205.82	4.809%	$215.7179	$215.72	$215.70	$215.70
Purchase #3	$183.52	9.243%	$200.4828	$200.48	$200.50	$200.50
Purchase #4	$101.44	7.504%	$109.0521	$109.05	$109.05	$109.10
Purchase #5	$125.77	11.647%	$140.4184	$140.42	$140.40	$140.40
Purchase #6	$95.29	12.127%	$106.8458	$106.85	$106.85	$106.80
Purchase #7	$126.95	10.584%	$140.3864	$140.39	$140.40	$140.40
7 purchase totals =	$1,062.56		$1,143.8363	$1,143.84	$1,143.85	$1,143.80