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	$42.85	12.641%	$48.2667	$48.27	$48.25	$48.30
Purchase #2	$50.71	13.572%	$57.5924	$57.59	$57.60	$57.60
Purchase #3	$24.89	9.188%	$27.1769	$27.18	$27.20	$27.20
Purchase #4	$93.84	10.292%	$103.498	$103.50	$103.50	$103.50
Purchase #5	$217.89	4.611%	$227.9369	$227.94	$227.95	$227.90
Purchase #6	$71.92	8.204%	$77.8203	$77.82	$77.80	$77.80
Purchase #7	$107.44	6.162%	$114.0605	$114.06	$114.05	$114.10
7 purchase totals =	$609.54		$656.3517	$656.36	$656.35	$656.40