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	$105.25	5.147%	$110.6672	$110.67	$110.65	$110.70
Purchase #2	$36.58	13.497%	$41.5172	$41.52	$41.50	$41.50
Purchase #3	$156.68	10.464%	$173.075	$173.08	$173.10	$173.10
Purchase #4	$74.92	4.208%	$78.0726	$78.07	$78.05	$78.10
Purchase #5	$177.43	12.457%	$199.5325	$199.53	$199.55	$199.50
Purchase #6	$153.28	9.608%	$168.0071	$168.01	$168.00	$168.00
Purchase #7	$184.90	8.554%	$200.7163	$200.72	$200.70	$200.70
7 purchase totals =	$889.04		$971.5879	$971.60	$971.55	$971.60