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	$72.75	9.140%	$79.3994	$79.40	$79.40	$79.40
Purchase #2	$59.82	11.334%	$66.6	$66.60	$66.60	$66.60
Purchase #3	$28.56	12.772%	$32.2077	$32.21	$32.20	$32.20
Purchase #4	$69.49	4.787%	$72.8165	$72.82	$72.80	$72.80
Purchase #5	$60.27	4.790%	$63.1569	$63.16	$63.15	$63.20
Purchase #6	$15.83	10.353%	$17.4689	$17.47	$17.45	$17.50
Purchase #7	$50.65	6.444%	$53.9139	$53.91	$53.90	$53.90
7 purchase totals =	$357.37		$385.5633	$385.57	$385.50	$385.60