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	$10.61	13.712%	$12.0648	$12.06	$12.05	$12.10
Purchase #2	$68.47	5.452%	$72.203	$72.20	$72.20	$72.20
Purchase #3	$112.30	10.261%	$123.8231	$123.82	$123.80	$123.80
Purchase #4	$62.72	5.250%	$66.0128	$66.01	$66.00	$66.00
Purchase #5	$213.72	6.353%	$227.2976	$227.30	$227.30	$227.30
Purchase #6	$111.54	10.744%	$123.5239	$123.52	$123.50	$123.50
Purchase #7	$27.76	4.824%	$29.0991	$29.10	$29.10	$29.10
7 purchase totals =	$607.12		$654.0243	$654.01	$653.95	$654.00