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	$75.39	11.233%	$83.8586	$83.86	$83.85	$83.90
Purchase #2	$88.53	7.758%	$95.3982	$95.40	$95.40	$95.40
Purchase #3	$147.43	7.658%	$158.7202	$158.72	$158.70	$158.70
Purchase #4	$111.95	5.826%	$118.4722	$118.47	$118.45	$118.50
Purchase #5	$119.60	6.501%	$127.3752	$127.38	$127.40	$127.40
Purchase #6	$6.78	8.303%	$7.3429	$7.34	$7.35	$7.30
Purchase #7	$166.36	6.433%	$177.0619	$177.06	$177.05	$177.10
7 purchase totals =	$716.04		$768.2292	$768.23	$768.20	$768.30