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	$39.29	10.466%	$43.4021	$43.40	$43.40	$43.40
Purchase #2	$134.94	13.627%	$153.3283	$153.33	$153.35	$153.30
Purchase #3	$86.97	5.645%	$91.8795	$91.88	$91.90	$91.90
Purchase #4	$219.75	13.698%	$249.8514	$249.85	$249.85	$249.90
Purchase #5	$151.98	8.596%	$165.0442	$165.04	$165.05	$165.00
Purchase #6	$103.52	4.447%	$108.1235	$108.12	$108.10	$108.10
Purchase #7	$244.69	4.495%	$255.6888	$255.69	$255.70	$255.70
7 purchase totals =	$981.14		$1,067.3178	$1,067.31	$1,067.35	$1,067.30