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	$114.38	11.754%	$127.8242	$127.82	$127.80	$127.80
Purchase #2	$23.35	8.650%	$25.3698	$25.37	$25.35	$25.40
Purchase #3	$86.60	4.560%	$90.549	$90.55	$90.55	$90.50
Purchase #4	$87.94	8.151%	$95.108	$95.11	$95.10	$95.10
Purchase #5	$154.78	5.145%	$162.7434	$162.74	$162.75	$162.70
Purchase #6	$137.59	5.856%	$145.6473	$145.65	$145.65	$145.60
Purchase #7	$70.28	5.809%	$74.3626	$74.36	$74.35	$74.40
7 purchase totals =	$674.92		$721.6043	$721.60	$721.55	$721.50