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	$113.64	12.130%	$127.4245	$127.42	$127.40	$127.40
Purchase #2	$220.59	11.596%	$246.1696	$246.17	$246.15	$246.20
Purchase #3	$230.64	11.388%	$256.9053	$256.91	$256.90	$256.90
Purchase #4	$193.30	7.573%	$207.9386	$207.94	$207.95	$207.90
Purchase #5	$99.49	5.128%	$104.5918	$104.59	$104.60	$104.60
Purchase #6	$196.40	11.275%	$218.5441	$218.54	$218.55	$218.50
Purchase #7	$176.50	7.592%	$189.8999	$189.90	$189.90	$189.90
7 purchase totals =	$1,230.56		$1,351.4738	$1,351.47	$1,351.45	$1,351.40