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	$80.51	3.761%	$83.538	$83.54	$83.55	$83.50
Purchase #2	$46.25	4.448%	$48.3072	$48.31	$48.30	$48.30
Purchase #3	$30.53	3.324%	$31.5448	$31.54	$31.55	$31.50
Purchase #4	$77.84	7.445%	$83.6352	$83.64	$83.65	$83.60
Purchase #5	$83.49	3.239%	$86.1942	$86.19	$86.20	$86.20
Purchase #6	$142.68	10.835%	$158.1394	$158.14	$158.15	$158.10
Purchase #7	$126.43	12.104%	$141.7331	$141.73	$141.75	$141.70
7 purchase totals =	$587.73		$633.0919	$633.09	$633.15	$632.90