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	$152.39	13.143%	$172.4186	$172.42	$172.40	$172.40
Purchase #2	$10.82	9.211%	$11.8166	$11.82	$11.80	$11.80
Purchase #3	$93.97	12.667%	$105.8732	$105.87	$105.85	$105.90
Purchase #4	$20.53	3.481%	$21.2446	$21.24	$21.25	$21.20
Purchase #5	$30.46	11.583%	$33.9882	$33.99	$34.00	$34.00
Purchase #6	$13.87	9.815%	$15.2313	$15.23	$15.25	$15.20
Purchase #7	$247.42	5.780%	$261.7209	$261.72	$261.70	$261.70
7 purchase totals =	$569.46		$622.2934	$622.29	$622.25	$622.20