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	$175.39	13.162%	$198.4748	$198.47	$198.45	$198.50
Purchase #2	$145.92	4.428%	$152.3813	$152.38	$152.40	$152.40
Purchase #3	$232.52	11.633%	$259.5691	$259.57	$259.55	$259.60
Purchase #4	$57.59	13.593%	$65.4182	$65.42	$65.40	$65.40
Purchase #5	$60.93	10.373%	$67.2503	$67.25	$67.25	$67.30
Purchase #6	$231.83	9.135%	$253.0077	$253.01	$253.00	$253.00
Purchase #7	$30.50	12.575%	$34.3354	$34.34	$34.35	$34.30
7 purchase totals =	$934.68		$1,030.4368	$1,030.44	$1,030.40	$1,030.50