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	$42.45	4.660%	$44.4282	$44.43	$44.45	$44.40
Purchase #2	$77.86	7.228%	$83.4877	$83.49	$83.50	$83.50
Purchase #3	$171.80	11.418%	$191.4161	$191.42	$191.40	$191.40
Purchase #4	$145.94	13.603%	$165.7922	$165.79	$165.80	$165.80
Purchase #5	$247.35	4.642%	$258.832	$258.83	$258.85	$258.80
Purchase #6	$27.47	6.694%	$29.3088	$29.31	$29.30	$29.30
Purchase #7	$111.76	13.240%	$126.557	$126.56	$126.55	$126.60
7 purchase totals =	$824.63		$899.8220	$899.83	$899.85	$899.80