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	$117.49	8.418%	$127.3803	$127.38	$127.40	$127.40
Purchase #2	$100.93	10.192%	$111.2168	$111.22	$111.20	$111.20
Purchase #3	$70.27	10.160%	$77.4094	$77.41	$77.40	$77.40
Purchase #4	$70.52	5.208%	$74.1927	$74.19	$74.20	$74.20
Purchase #5	$108.88	6.365%	$115.8102	$115.81	$115.80	$115.80
Purchase #6	$168.62	9.760%	$185.0773	$185.08	$185.10	$185.10
Purchase #7	$127.58	7.667%	$137.3616	$137.36	$137.35	$137.40
7 purchase totals =	$764.29		$828.4483	$828.45	$828.45	$828.50