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	$136.25	12.341%	$153.0646	$153.06	$153.05	$153.10
Purchase #2	$47.57	9.269%	$51.9793	$51.98	$52.00	$52.00
Purchase #3	$92.53	13.623%	$105.1354	$105.14	$105.15	$105.10
Purchase #4	$42.81	12.361%	$48.1017	$48.10	$48.10	$48.10
Purchase #5	$192.61	10.170%	$212.1984	$212.20	$212.20	$212.20
Purchase #6	$42.97	7.294%	$46.1042	$46.10	$46.10	$46.10
Purchase #7	$53.29	11.808%	$59.5825	$59.58	$59.60	$59.60
7 purchase totals =	$608.03		$676.1661	$676.16	$676.20	$676.20