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	$168.97	11.278%	$188.0264	$188.03	$188.05	$188.00
Purchase #2	$204.34	11.269%	$227.3671	$227.37	$227.35	$227.40
Purchase #3	$108.85	3.204%	$112.3376	$112.34	$112.35	$112.30
Purchase #4	$82.55	4.149%	$85.975	$85.98	$86.00	$86.00
Purchase #5	$103.90	7.414%	$111.6031	$111.60	$111.60	$111.60
Purchase #6	$134.82	13.818%	$153.4494	$153.45	$153.45	$153.40
Purchase #7	$9.97	13.303%	$11.2963	$11.30	$11.30	$11.30
7 purchase totals =	$813.40		$890.0549	$890.07	$890.10	$890.00