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	$12.73	9.461%	$13.9344	$13.93	$13.95	$13.90
Purchase #2	$85.82	3.699%	$88.9945	$88.99	$89.00	$89.00
Purchase #3	$116.98	8.117%	$126.4753	$126.48	$126.50	$126.50
Purchase #4	$108.54	13.704%	$123.4143	$123.41	$123.40	$123.40
Purchase #5	$99.75	12.119%	$111.8387	$111.84	$111.85	$111.80
Purchase #6	$133.33	3.462%	$137.9459	$137.95	$137.95	$137.90
Purchase #7	$146.75	11.376%	$163.4443	$163.44	$163.45	$163.40
7 purchase totals =	$703.90		$766.0474	$766.04	$766.10	$765.90