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	$54.66	5.446%	$57.6368	$57.64	$57.65	$57.60
Purchase #2	$9.69	11.119%	$10.7674	$10.77	$10.75	$10.80
Purchase #3	$144.52	7.152%	$154.8561	$154.86	$154.85	$154.90
Purchase #4	$35.34	12.821%	$39.8709	$39.87	$39.85	$39.90
Purchase #5	$131.89	9.540%	$144.4723	$144.47	$144.45	$144.50
Purchase #6	$92.27	8.800%	$100.3898	$100.39	$100.40	$100.40
Purchase #7	$229.64	5.259%	$241.7168	$241.72	$241.70	$241.70
7 purchase totals =	$698.01		$749.7101	$749.72	$749.65	$749.80