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	$178.71	3.659%	$185.249	$185.25	$185.25	$185.20
Purchase #2	$230.60	10.189%	$254.0958	$254.10	$254.10	$254.10
Purchase #3	$152.51	5.204%	$160.4466	$160.45	$160.45	$160.40
Purchase #4	$167.66	3.265%	$173.1341	$173.13	$173.15	$173.10
Purchase #5	$80.84	11.196%	$89.8908	$89.89	$89.90	$89.90
Purchase #6	$41.48	6.491%	$44.1725	$44.17	$44.15	$44.20
Purchase #7	$103.32	3.516%	$106.9527	$106.95	$106.95	$107.00
7 purchase totals =	$955.12		$1,013.9415	$1,013.94	$1,013.95	$1,013.90