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	$99.77	8.245%	$107.996	$108.00	$108.00	$108.00
Purchase #2	$196.88	10.278%	$217.1153	$217.12	$217.10	$217.10
Purchase #3	$66.80	9.809%	$73.3524	$73.35	$73.35	$73.40
Purchase #4	$188.31	4.393%	$196.5825	$196.58	$196.60	$196.60
Purchase #5	$10.37	12.108%	$11.6256	$11.63	$11.65	$11.60
Purchase #6	$95.30	8.326%	$103.2347	$103.23	$103.25	$103.20
Purchase #7	$51.83	11.565%	$57.8241	$57.82	$57.80	$57.80
7 purchase totals =	$709.26		$767.7306	$767.73	$767.75	$767.70