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	$85.72	3.496%	$88.7168	$88.72	$88.70	$88.70
Purchase #2	$75.89	11.485%	$84.606	$84.61	$84.60	$84.60
Purchase #3	$148.45	4.211%	$154.7012	$154.70	$154.70	$154.70
Purchase #4	$159.60	11.188%	$177.456	$177.46	$177.45	$177.50
Purchase #5	$119.42	6.380%	$127.039	$127.04	$127.05	$127.00
Purchase #6	$114.72	7.555%	$123.3871	$123.39	$123.40	$123.40
Purchase #7	$148.81	6.820%	$158.9588	$158.96	$158.95	$159.00
7 purchase totals =	$852.61		$914.8649	$914.88	$914.85	$914.90