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	$178.60	11.324%	$198.8247	$198.82	$198.80	$198.80
Purchase #2	$41.93	5.404%	$44.1959	$44.20	$44.20	$44.20
Purchase #3	$154.84	6.219%	$164.4695	$164.47	$164.45	$164.50
Purchase #4	$64.59	11.678%	$72.1328	$72.13	$72.15	$72.10
Purchase #5	$49.62	11.750%	$55.4504	$55.45	$55.45	$55.50
Purchase #6	$22.83	8.759%	$24.8297	$24.83	$24.85	$24.80
Purchase #7	$112.81	6.108%	$119.7004	$119.70	$119.70	$119.70
7 purchase totals =	$625.22		$679.6034	$679.60	$679.60	$679.60