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	$204.96	9.134%	$223.681	$223.68	$223.70	$223.70
Purchase #2	$215.83	6.829%	$230.569	$230.57	$230.55	$230.60
Purchase #3	$158.80	8.856%	$172.8633	$172.86	$172.85	$172.90
Purchase #4	$74.90	12.576%	$84.3194	$84.32	$84.30	$84.30
Purchase #5	$18.85	11.689%	$21.0534	$21.05	$21.05	$21.10
Purchase #6	$167.30	13.602%	$190.0561	$190.06	$190.05	$190.10
Purchase #7	$72.94	7.857%	$78.6709	$78.67	$78.65	$78.70
7 purchase totals =	$913.58		$1,001.2131	$1,001.21	$1,001.15	$1,001.40