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	$103.64	7.860%	$111.7861	$111.79	$111.80	$111.80
Purchase #2	$208.52	6.353%	$221.7673	$221.77	$221.75	$221.80
Purchase #3	$13.43	12.267%	$15.0775	$15.08	$15.10	$15.10
Purchase #4	$146.92	11.839%	$164.3139	$164.31	$164.30	$164.30
Purchase #5	$64.59	3.141%	$66.6188	$66.62	$66.60	$66.60
Purchase #6	$151.37	9.824%	$166.2406	$166.24	$166.25	$166.20
Purchase #7	$62.97	7.700%	$67.8187	$67.82	$67.80	$67.80
7 purchase totals =	$751.44		$813.6229	$813.63	$813.60	$813.60