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	$248.45	4.468%	$259.5507	$259.55	$259.55	$259.60
Purchase #2	$151.85	13.420%	$172.2283	$172.23	$172.25	$172.20
Purchase #3	$15.59	5.420%	$16.435	$16.44	$16.45	$16.40
Purchase #4	$212.97	9.680%	$233.5855	$233.59	$233.60	$233.60
Purchase #5	$86.49	3.594%	$89.5985	$89.60	$89.60	$89.60
Purchase #6	$162.52	5.119%	$170.8394	$170.84	$170.85	$170.80
Purchase #7	$157.49	9.733%	$172.8185	$172.82	$172.80	$172.80
7 purchase totals =	$1,035.36		$1,115.0559	$1,115.07	$1,115.10	$1,115.00