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	$153.25	12.528%	$172.4492	$172.45	$172.45	$172.40
Purchase #2	$246.85	13.235%	$279.5206	$279.52	$279.50	$279.50
Purchase #3	$127.32	11.499%	$141.9605	$141.96	$141.95	$142.00
Purchase #4	$66.69	5.521%	$70.372	$70.37	$70.35	$70.40
Purchase #5	$87.60	3.828%	$90.9533	$90.95	$90.95	$91.00
Purchase #6	$191.43	4.738%	$200.5	$200.50	$200.50	$200.50
Purchase #7	$97.29	9.229%	$106.2689	$106.27	$106.25	$106.30
7 purchase totals =	$970.43		$1,062.0245	$1,062.02	$1,061.95	$1,062.10