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	$67.49	5.378%	$71.1196	$71.12	$71.10	$71.10
Purchase #2	$67.44	7.678%	$72.618	$72.62	$72.60	$72.60
Purchase #3	$25.27	11.678%	$28.221	$28.22	$28.20	$28.20
Purchase #4	$34.87	13.408%	$39.5454	$39.55	$39.55	$39.50
Purchase #5	$215.86	6.376%	$229.6232	$229.62	$229.60	$229.60
Purchase #6	$166.85	3.494%	$172.6797	$172.68	$172.70	$172.70
Purchase #7	$61.80	8.660%	$67.1519	$67.15	$67.15	$67.20
7 purchase totals =	$639.58		$680.9588	$680.96	$680.90	$680.90