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	$216.31	5.788%	$228.83	$228.83	$228.85	$228.80
Purchase #2	$40.82	3.575%	$42.2793	$42.28	$42.30	$42.30
Purchase #3	$108.70	4.182%	$113.2458	$113.25	$113.25	$113.20
Purchase #4	$99.45	3.665%	$103.0948	$103.09	$103.10	$103.10
Purchase #5	$88.64	13.663%	$100.7509	$100.75	$100.75	$100.80
Purchase #6	$247.85	7.726%	$266.9989	$267.00	$267.00	$267.00
Purchase #7	$109.51	13.344%	$124.123	$124.12	$124.10	$124.10
7 purchase totals =	$911.28		$979.3227	$979.32	$979.35	$979.30