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	$158.25	6.568%	$168.6439	$168.64	$168.65	$168.60
Purchase #2	$49.27	8.739%	$53.5757	$53.58	$53.60	$53.60
Purchase #3	$80.85	9.870%	$88.8299	$88.83	$88.85	$88.80
Purchase #4	$106.31	7.414%	$114.1918	$114.19	$114.20	$114.20
Purchase #5	$108.82	5.273%	$114.5581	$114.56	$114.55	$114.60
Purchase #6	$199.87	4.386%	$208.6363	$208.64	$208.65	$208.60
Purchase #7	$10.98	8.711%	$11.9365	$11.94	$11.95	$11.90
7 purchase totals =	$714.35		$760.3722	$760.38	$760.45	$760.30