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	$67.45	10.289%	$74.3899	$74.39	$74.40	$74.40
Purchase #2	$104.77	11.538%	$116.8584	$116.86	$116.85	$116.90
Purchase #3	$127.78	11.244%	$142.1476	$142.15	$142.15	$142.10
Purchase #4	$85.42	10.617%	$94.489	$94.49	$94.50	$94.50
Purchase #5	$188.51	13.644%	$214.2303	$214.23	$214.25	$214.20
Purchase #6	$208.59	13.806%	$237.3879	$237.39	$237.40	$237.40
Purchase #7	$28.27	4.572%	$29.5625	$29.56	$29.55	$29.60
7 purchase totals =	$810.79		$909.0656	$909.07	$909.10	$909.10