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	$49.74	10.240%	$54.8334	$54.83	$54.85	$54.80
Purchase #2	$54.60	3.491%	$56.5061	$56.51	$56.50	$56.50
Purchase #3	$226.87	11.660%	$253.323	$253.32	$253.30	$253.30
Purchase #4	$139.81	3.414%	$144.5831	$144.58	$144.60	$144.60
Purchase #5	$83.36	8.644%	$90.5656	$90.57	$90.55	$90.60
Purchase #6	$76.96	3.426%	$79.5966	$79.60	$79.60	$79.60
Purchase #7	$174.80	7.558%	$188.0114	$188.01	$188.00	$188.00
7 purchase totals =	$806.14		$867.4192	$867.42	$867.40	$867.40