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	$12.59	11.669%	$14.0591	$14.06	$14.05	$14.10
Purchase #2	$148.27	3.406%	$153.3201	$153.32	$153.30	$153.30
Purchase #3	$37.26	5.485%	$39.3037	$39.30	$39.30	$39.30
Purchase #4	$152.83	13.539%	$173.5217	$173.52	$173.50	$173.50
Purchase #5	$215.36	8.719%	$234.1372	$234.14	$234.15	$234.10
Purchase #6	$19.94	6.838%	$21.3035	$21.30	$21.30	$21.30
Purchase #7	$55.60	12.570%	$62.5889	$62.59	$62.60	$62.60
7 purchase totals =	$641.85		$698.2342	$698.23	$698.20	$698.20