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	$44.25	10.573%	$48.9286	$48.93	$48.95	$48.90
Purchase #2	$233.93	8.554%	$253.9404	$253.94	$253.95	$253.90
Purchase #3	$151.87	13.666%	$172.6246	$172.62	$172.60	$172.60
Purchase #4	$96.99	13.260%	$109.8509	$109.85	$109.85	$109.90
Purchase #5	$24.98	13.568%	$28.3693	$28.37	$28.35	$28.40
Purchase #6	$96.95	4.237%	$101.0578	$101.06	$101.05	$101.10
Purchase #7	$104.71	13.167%	$118.4972	$118.50	$118.50	$118.50
7 purchase totals =	$753.68		$833.2688	$833.27	$833.25	$833.30