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	$66.94	6.540%	$71.3179	$71.32	$71.30	$71.30
Purchase #2	$173.83	13.212%	$196.7964	$196.80	$196.80	$196.80
Purchase #3	$153.72	8.103%	$166.1759	$166.18	$166.20	$166.20
Purchase #4	$148.96	7.602%	$160.2839	$160.28	$160.30	$160.30
Purchase #5	$196.87	8.806%	$214.2064	$214.21	$214.20	$214.20
Purchase #6	$95.87	5.409%	$101.0556	$101.06	$101.05	$101.10
Purchase #7	$158.96	10.193%	$175.1628	$175.16	$175.15	$175.20
7 purchase totals =	$995.15		$1,084.9989	$1,085.01	$1,085.00	$1,085.10