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	$31.84	6.663%	$33.9615	$33.96	$33.95	$34.00
Purchase #2	$165.49	10.766%	$183.3067	$183.31	$183.30	$183.30
Purchase #3	$178.68	12.271%	$200.6058	$200.61	$200.60	$200.60
Purchase #4	$101.95	8.859%	$110.9818	$110.98	$111.00	$111.00
Purchase #5	$234.90	13.283%	$266.1018	$266.10	$266.10	$266.10
Purchase #6	$167.81	4.337%	$175.0879	$175.09	$175.10	$175.10
Purchase #7	$94.79	3.832%	$98.4224	$98.42	$98.40	$98.40
7 purchase totals =	$975.46		$1,068.4679	$1,068.47	$1,068.45	$1,068.50