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	$112.28	12.859%	$126.7181	$126.72	$126.70	$126.70
Purchase #2	$131.73	10.383%	$145.4075	$145.41	$145.40	$145.40
Purchase #3	$63.78	4.365%	$66.564	$66.56	$66.55	$66.60
Purchase #4	$195.71	8.429%	$212.2064	$212.21	$212.20	$212.20
Purchase #5	$75.56	10.795%	$83.7167	$83.72	$83.70	$83.70
Purchase #6	$175.72	11.704%	$196.2863	$196.29	$196.30	$196.30
Purchase #7	$11.46	10.733%	$12.69	$12.69	$12.70	$12.70
7 purchase totals =	$766.24		$843.5890	$843.60	$843.55	$843.60