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	$121.31	4.854%	$127.1984	$127.20	$127.20	$127.20
Purchase #2	$243.28	11.262%	$270.6782	$270.68	$270.70	$270.70
Purchase #3	$160.79	8.170%	$173.9265	$173.93	$173.95	$173.90
Purchase #4	$15.68	6.644%	$16.7218	$16.72	$16.70	$16.70
Purchase #5	$156.99	10.583%	$173.6043	$173.60	$173.60	$173.60
Purchase #6	$183.59	3.278%	$189.6081	$189.61	$189.60	$189.60
Purchase #7	$103.43	5.829%	$109.4589	$109.46	$109.45	$109.50
7 purchase totals =	$985.07		$1,061.1962	$1,061.20	$1,061.20	$1,061.20