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	$72.65	12.776%	$81.9318	$81.93	$81.95	$81.90
Purchase #2	$72.89	7.855%	$78.6155	$78.62	$78.60	$78.60
Purchase #3	$173.81	3.484%	$179.8655	$179.87	$179.85	$179.90
Purchase #4	$16.38	6.569%	$17.456	$17.46	$17.45	$17.50
Purchase #5	$104.79	13.543%	$118.9817	$118.98	$119.00	$119.00
Purchase #6	$28.87	10.812%	$31.9914	$31.99	$32.00	$32.00
Purchase #7	$208.86	9.479%	$228.6578	$228.66	$228.65	$228.70
7 purchase totals =	$678.25		$737.4997	$737.51	$737.50	$737.60