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	$40.82	13.712%	$46.4172	$46.42	$46.40	$46.40
Purchase #2	$141.35	4.794%	$148.1263	$148.13	$148.15	$148.10
Purchase #3	$49.45	12.651%	$55.7059	$55.71	$55.70	$55.70
Purchase #4	$52.96	7.250%	$56.7996	$56.80	$56.80	$56.80
Purchase #5	$41.56	9.730%	$45.6038	$45.60	$45.60	$45.60
Purchase #6	$163.72	3.651%	$169.6974	$169.70	$169.70	$169.70
Purchase #7	$70.31	3.312%	$72.6387	$72.64	$72.65	$72.60
7 purchase totals =	$560.17		$594.9889	$595.00	$595.00	$594.90