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	$26.69	9.669%	$29.2707	$29.27	$29.25	$29.30
Purchase #2	$10.57	11.786%	$11.8158	$11.82	$11.80	$11.80
Purchase #3	$213.63	13.679%	$242.8524	$242.85	$242.85	$242.90
Purchase #4	$233.83	9.512%	$256.0719	$256.07	$256.05	$256.10
Purchase #5	$155.33	13.848%	$176.8401	$176.84	$176.85	$176.80
Purchase #6	$149.41	11.188%	$166.126	$166.13	$166.15	$166.10
Purchase #7	$105.49	5.780%	$111.5873	$111.59	$111.60	$111.60
7 purchase totals =	$894.95		$994.5642	$994.57	$994.55	$994.60