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	$192.54	6.529%	$205.1109	$205.11	$205.10	$205.10
Purchase #2	$30.94	5.241%	$32.5616	$32.56	$32.55	$32.60
Purchase #3	$25.47	6.398%	$27.0996	$27.10	$27.10	$27.10
Purchase #4	$128.70	12.230%	$144.44	$144.44	$144.45	$144.40
Purchase #5	$153.78	10.541%	$169.9899	$169.99	$170.00	$170.00
Purchase #6	$88.62	13.651%	$100.7175	$100.72	$100.70	$100.70
Purchase #7	$36.92	4.559%	$38.6032	$38.60	$38.60	$38.60
7 purchase totals =	$656.97		$718.5227	$718.52	$718.50	$718.50