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	$138.92	5.676%	$146.8051	$146.81	$146.80	$146.80
Purchase #2	$165.67	4.866%	$173.7315	$173.73	$173.75	$173.70
Purchase #3	$43.91	6.271%	$46.6636	$46.66	$46.65	$46.70
Purchase #4	$105.72	4.626%	$110.6106	$110.61	$110.60	$110.60
Purchase #5	$183.63	6.249%	$195.105	$195.11	$195.10	$195.10
Purchase #6	$100.92	12.461%	$113.4956	$113.50	$113.50	$113.50
Purchase #7	$219.93	4.817%	$230.524	$230.52	$230.50	$230.50
7 purchase totals =	$958.70		$1,016.9354	$1,016.94	$1,016.90	$1,016.90