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	$49.73	7.763%	$53.5905	$53.59	$53.60	$53.60
Purchase #2	$42.29	7.525%	$45.4723	$45.47	$45.45	$45.50
Purchase #3	$28.60	12.733%	$32.2416	$32.24	$32.25	$32.20
Purchase #4	$125.93	3.499%	$130.3363	$130.34	$130.35	$130.30
Purchase #5	$108.75	7.483%	$116.8878	$116.89	$116.90	$116.90
Purchase #6	$25.84	11.531%	$28.8196	$28.82	$28.80	$28.80
Purchase #7	$48.52	11.491%	$54.0954	$54.10	$54.10	$54.10
7 purchase totals =	$429.66		$461.4435	$461.45	$461.45	$461.40