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	$150.43	12.232%	$168.8306	$168.83	$168.85	$168.80
Purchase #2	$72.39	3.146%	$74.6674	$74.67	$74.65	$74.70
Purchase #3	$54.45	10.636%	$60.2413	$60.24	$60.25	$60.20
Purchase #4	$96.82	7.709%	$104.2839	$104.28	$104.30	$104.30
Purchase #5	$90.39	5.347%	$95.2232	$95.22	$95.20	$95.20
Purchase #6	$215.90	10.244%	$238.0168	$238.02	$238.00	$238.00
Purchase #7	$214.51	3.760%	$222.5756	$222.58	$222.60	$222.60
7 purchase totals =	$894.89		$963.8388	$963.84	$963.85	$963.80