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	$148.50	6.840%	$158.6574	$158.66	$158.65	$158.70
Purchase #2	$107.82	11.157%	$119.8495	$119.85	$119.85	$119.80
Purchase #3	$157.31	5.253%	$165.5735	$165.57	$165.55	$165.60
Purchase #4	$133.72	9.826%	$146.8593	$146.86	$146.85	$146.90
Purchase #5	$122.38	7.705%	$131.8094	$131.81	$131.80	$131.80
Purchase #6	$63.40	4.646%	$66.3456	$66.35	$66.35	$66.30
Purchase #7	$70.95	8.723%	$77.139	$77.14	$77.15	$77.10
7 purchase totals =	$804.08		$866.2337	$866.24	$866.20	$866.20