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	$49.91	8.461%	$54.1329	$54.13	$54.15	$54.10
Purchase #2	$171.56	11.184%	$190.7473	$190.75	$190.75	$190.70
Purchase #3	$201.36	12.558%	$226.6468	$226.65	$226.65	$226.60
Purchase #4	$68.52	5.167%	$72.0604	$72.06	$72.05	$72.10
Purchase #5	$196.83	7.507%	$211.606	$211.61	$211.60	$211.60
Purchase #6	$45.46	5.858%	$48.123	$48.12	$48.10	$48.10
Purchase #7	$17.79	9.571%	$19.4927	$19.49	$19.50	$19.50
7 purchase totals =	$751.43		$822.8091	$822.81	$822.80	$822.70