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	$39.79	4.410%	$41.5447	$41.54	$41.55	$41.50
Purchase #2	$86.39	11.851%	$96.6281	$96.63	$96.65	$96.60
Purchase #3	$214.89	4.457%	$224.4676	$224.47	$224.45	$224.50
Purchase #4	$68.57	11.463%	$76.4302	$76.43	$76.45	$76.40
Purchase #5	$126.37	13.724%	$143.713	$143.71	$143.70	$143.70
Purchase #6	$165.78	7.791%	$178.6959	$178.70	$178.70	$178.70
Purchase #7	$100.90	10.506%	$111.5006	$111.50	$111.50	$111.50
7 purchase totals =	$802.69		$872.9801	$872.98	$873.00	$872.90