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	$146.71	7.614%	$157.8805	$157.88	$157.90	$157.90
Purchase #2	$127.82	3.526%	$132.3269	$132.33	$132.35	$132.30
Purchase #3	$17.45	11.311%	$19.4238	$19.42	$19.40	$19.40
Purchase #4	$210.87	13.179%	$238.6606	$238.66	$238.65	$238.70
Purchase #5	$220.39	6.718%	$235.1958	$235.20	$235.20	$235.20
Purchase #6	$115.80	10.127%	$127.5271	$127.53	$127.55	$127.50
Purchase #7	$167.88	10.512%	$185.5275	$185.53	$185.55	$185.50
7 purchase totals =	$1,006.92		$1,096.5422	$1,096.55	$1,096.60	$1,096.50