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	$148.51	12.368%	$166.8777	$166.88	$166.90	$166.90
Purchase #2	$132.29	3.773%	$137.2813	$137.28	$137.30	$137.30
Purchase #3	$111.66	5.868%	$118.2122	$118.21	$118.20	$118.20
Purchase #4	$93.89	5.804%	$99.3394	$99.34	$99.35	$99.30
Purchase #5	$72.99	10.730%	$80.8218	$80.82	$80.80	$80.80
Purchase #6	$48.94	10.582%	$54.1188	$54.12	$54.10	$54.10
Purchase #7	$63.81	7.514%	$68.6047	$68.60	$68.60	$68.60
7 purchase totals =	$672.09		$725.2559	$725.25	$725.25	$725.20