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	$173.86	3.453%	$179.8634	$179.86	$179.85	$179.90
Purchase #2	$9.34	9.551%	$10.2321	$10.23	$10.25	$10.20
Purchase #3	$217.29	5.549%	$229.3474	$229.35	$229.35	$229.30
Purchase #4	$146.57	4.866%	$153.7021	$153.70	$153.70	$153.70
Purchase #5	$200.88	8.423%	$217.8001	$217.80	$217.80	$217.80
Purchase #6	$160.86	8.704%	$174.8613	$174.86	$174.85	$174.90
Purchase #7	$137.67	10.772%	$152.4998	$152.50	$152.50	$152.50
7 purchase totals =	$1,046.47		$1,118.3062	$1,118.30	$1,118.30	$1,118.30