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	$63.88	5.269%	$67.2458	$67.25	$67.25	$67.20
Purchase #2	$101.92	3.725%	$105.7165	$105.72	$105.70	$105.70
Purchase #3	$141.48	3.748%	$146.7827	$146.78	$146.80	$146.80
Purchase #4	$35.39	10.527%	$39.1155	$39.12	$39.10	$39.10
Purchase #5	$193.27	12.810%	$218.0279	$218.03	$218.05	$218.00
Purchase #6	$53.86	3.548%	$55.771	$55.77	$55.75	$55.80
Purchase #7	$99.27	5.597%	$104.8261	$104.83	$104.85	$104.80
7 purchase totals =	$689.07		$737.4855	$737.50	$737.50	$737.40