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	$109.30	12.406%	$122.8598	$122.86	$122.85	$122.90
Purchase #2	$228.64	8.845%	$248.8632	$248.86	$248.85	$248.90
Purchase #3	$71.51	4.607%	$74.8045	$74.80	$74.80	$74.80
Purchase #4	$65.64	10.251%	$72.3688	$72.37	$72.35	$72.40
Purchase #5	$150.32	5.657%	$158.8236	$158.82	$158.80	$158.80
Purchase #6	$217.55	7.515%	$233.8989	$233.90	$233.90	$233.90
Purchase #7	$155.96	11.601%	$174.0529	$174.05	$174.05	$174.10
7 purchase totals =	$998.92		$1,085.6717	$1,085.66	$1,085.60	$1,085.80