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	$249.78	5.245%	$262.881	$262.88	$262.90	$262.90
Purchase #2	$126.77	11.302%	$141.0975	$141.10	$141.10	$141.10
Purchase #3	$26.87	9.616%	$29.4538	$29.45	$29.45	$29.50
Purchase #4	$222.82	13.369%	$252.6088	$252.61	$252.60	$252.60
Purchase #5	$137.46	3.169%	$141.8161	$141.82	$141.80	$141.80
Purchase #6	$164.72	3.864%	$171.0848	$171.08	$171.10	$171.10
Purchase #7	$94.68	4.426%	$98.8705	$98.87	$98.85	$98.90
7 purchase totals =	$1,023.10		$1,097.8125	$1,097.81	$1,097.80	$1,097.90