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	$85.99	11.169%	$95.5942	$95.59	$95.60	$95.60
Purchase #2	$14.58	12.429%	$16.3921	$16.39	$16.40	$16.40
Purchase #3	$90.59	9.817%	$99.4832	$99.48	$99.50	$99.50
Purchase #4	$222.31	13.831%	$253.0577	$253.06	$253.05	$253.10
Purchase #5	$38.29	9.207%	$41.8154	$41.82	$41.80	$41.80
Purchase #6	$184.64	10.548%	$204.1158	$204.12	$204.10	$204.10
Purchase #7	$105.52	3.635%	$109.3557	$109.36	$109.35	$109.40
7 purchase totals =	$741.92		$819.8141	$819.82	$819.80	$819.90