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	$31.86	8.359%	$34.5232	$34.52	$34.50	$34.50
Purchase #2	$108.87	3.564%	$112.7501	$112.75	$112.75	$112.80
Purchase #3	$6.79	8.284%	$7.3525	$7.35	$7.35	$7.40
Purchase #4	$117.75	8.420%	$127.6646	$127.66	$127.65	$127.70
Purchase #5	$95.37	4.483%	$99.6454	$99.65	$99.65	$99.60
Purchase #6	$214.87	3.655%	$222.7235	$222.72	$222.70	$222.70
Purchase #7	$168.40	5.837%	$178.2295	$178.23	$178.25	$178.20
7 purchase totals =	$743.91		$782.8888	$782.88	$782.85	$782.90