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	$10.77	8.699%	$11.7069	$11.71	$11.70	$11.70
Purchase #2	$55.56	13.603%	$63.1178	$63.12	$63.10	$63.10
Purchase #3	$94.96	13.176%	$107.4719	$107.47	$107.45	$107.50
Purchase #4	$53.78	13.578%	$61.0822	$61.08	$61.10	$61.10
Purchase #5	$68.80	10.531%	$76.0453	$76.05	$76.05	$76.00
Purchase #6	$98.61	13.199%	$111.6255	$111.63	$111.65	$111.60
Purchase #7	$165.91	11.659%	$185.2534	$185.25	$185.25	$185.30
7 purchase totals =	$548.39		$616.3030	$616.31	$616.30	$616.30