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	$60.75	10.121%	$66.8985	$66.90	$66.90	$66.90
Purchase #2	$195.83	7.143%	$209.8181	$209.82	$209.80	$209.80
Purchase #3	$101.41	4.156%	$105.6246	$105.62	$105.60	$105.60
Purchase #4	$56.66	3.196%	$58.4709	$58.47	$58.45	$58.50
Purchase #5	$13.77	10.462%	$15.2106	$15.21	$15.20	$15.20
Purchase #6	$228.95	8.459%	$248.3169	$248.32	$248.30	$248.30
Purchase #7	$51.51	9.358%	$56.3303	$56.33	$56.35	$56.30
7 purchase totals =	$708.88		$760.6699	$760.67	$760.60	$760.60