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	$14.56	7.508%	$15.6532	$15.65	$15.65	$15.70
Purchase #2	$222.96	7.325%	$239.2918	$239.29	$239.30	$239.30
Purchase #3	$39.94	12.630%	$44.9844	$44.98	$45.00	$45.00
Purchase #4	$83.32	7.629%	$89.6765	$89.68	$89.70	$89.70
Purchase #5	$98.40	6.517%	$104.8127	$104.81	$104.80	$104.80
Purchase #6	$48.91	8.719%	$53.1745	$53.17	$53.15	$53.20
Purchase #7	$120.70	5.611%	$127.4725	$127.47	$127.45	$127.50
7 purchase totals =	$628.79		$675.0656	$675.05	$675.05	$675.20