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	$63.59	9.474%	$69.6145	$69.61	$69.60	$69.60
Purchase #2	$92.65	12.476%	$104.209	$104.21	$104.20	$104.20
Purchase #3	$102.66	13.505%	$116.5242	$116.52	$116.50	$116.50
Purchase #4	$99.37	12.489%	$111.7803	$111.78	$111.80	$111.80
Purchase #5	$102.90	5.501%	$108.5605	$108.56	$108.55	$108.60
Purchase #6	$23.43	4.578%	$24.5026	$24.50	$24.50	$24.50
Purchase #7	$37.94	6.749%	$40.5006	$40.50	$40.50	$40.50
7 purchase totals =	$522.54		$575.6917	$575.68	$575.65	$575.70