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	$214.71	3.656%	$222.5598	$222.56	$222.55	$222.60
Purchase #2	$77.56	13.491%	$88.0236	$88.02	$88.00	$88.00
Purchase #3	$72.87	6.719%	$77.7661	$77.77	$77.75	$77.80
Purchase #4	$178.93	4.361%	$186.7331	$186.73	$186.75	$186.70
Purchase #5	$79.88	13.160%	$90.3922	$90.39	$90.40	$90.40
Purchase #6	$108.48	9.133%	$118.3875	$118.39	$118.40	$118.40
Purchase #7	$165.72	9.594%	$181.6192	$181.62	$181.60	$181.60
7 purchase totals =	$898.15		$965.4815	$965.48	$965.45	$965.50