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	$32.55	13.434%	$36.9228	$36.92	$36.90	$36.90
Purchase #2	$107.41	4.676%	$112.4325	$112.43	$112.45	$112.40
Purchase #3	$115.98	9.733%	$127.2683	$127.27	$127.25	$127.30
Purchase #4	$200.38	7.318%	$215.0438	$215.04	$215.05	$215.00
Purchase #5	$156.55	5.662%	$165.4139	$165.41	$165.40	$165.40
Purchase #6	$49.84	8.601%	$54.1267	$54.13	$54.15	$54.10
Purchase #7	$215.68	8.385%	$233.7648	$233.76	$233.75	$233.80
7 purchase totals =	$878.39		$944.9728	$944.96	$944.95	$944.90