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	$172.53	9.727%	$189.312	$189.31	$189.30	$189.30
Purchase #2	$49.49	10.195%	$54.5355	$54.54	$54.55	$54.50
Purchase #3	$32.45	3.614%	$33.6227	$33.62	$33.60	$33.60
Purchase #4	$155.71	3.289%	$160.8313	$160.83	$160.85	$160.80
Purchase #5	$85.88	5.735%	$90.8052	$90.81	$90.80	$90.80
Purchase #6	$171.87	9.679%	$188.5053	$188.51	$188.50	$188.50
Purchase #7	$17.56	11.843%	$19.6396	$19.64	$19.65	$19.60
7 purchase totals =	$685.49		$737.2516	$737.26	$737.25	$737.10