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	$102.77	6.139%	$109.0791	$109.08	$109.10	$109.10
Purchase #2	$202.71	7.181%	$217.2666	$217.27	$217.25	$217.30
Purchase #3	$52.54	5.566%	$55.4644	$55.46	$55.45	$55.50
Purchase #4	$178.51	12.477%	$200.7827	$200.78	$200.80	$200.80
Purchase #5	$16.89	8.381%	$18.3056	$18.31	$18.30	$18.30
Purchase #6	$7.45	3.784%	$7.7319	$7.73	$7.75	$7.70
Purchase #7	$133.70	10.817%	$148.1623	$148.16	$148.15	$148.20
7 purchase totals =	$694.57		$756.7926	$756.79	$756.80	$756.90