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	$37.84	8.763%	$41.1559	$41.16	$41.15	$41.20
Purchase #2	$13.90	6.712%	$14.833	$14.83	$14.85	$14.80
Purchase #3	$51.96	9.619%	$56.958	$56.96	$56.95	$57.00
Purchase #4	$34.86	7.486%	$37.4696	$37.47	$37.45	$37.50
Purchase #5	$106.99	4.357%	$111.6516	$111.65	$111.65	$111.70
Purchase #6	$33.30	11.272%	$37.0536	$37.05	$37.05	$37.10
Purchase #7	$178.70	4.839%	$187.3473	$187.35	$187.35	$187.30
7 purchase totals =	$457.55		$486.4690	$486.47	$486.45	$486.60