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	$112.86	3.482%	$116.7898	$116.79	$116.80	$116.80
Purchase #2	$36.85	5.733%	$38.9626	$38.96	$38.95	$39.00
Purchase #3	$95.32	10.743%	$105.5602	$105.56	$105.55	$105.60
Purchase #4	$204.66	6.568%	$218.1021	$218.10	$218.10	$218.10
Purchase #5	$70.98	8.657%	$77.1247	$77.12	$77.10	$77.10
Purchase #6	$198.35	13.836%	$225.7937	$225.79	$225.80	$225.80
Purchase #7	$210.83	10.821%	$233.6439	$233.64	$233.65	$233.60
7 purchase totals =	$929.85		$1,015.9770	$1,015.96	$1,015.95	$1,016.00