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	$43.29	7.711%	$46.6281	$46.63	$46.65	$46.60
Purchase #2	$158.29	11.770%	$176.9207	$176.92	$176.90	$176.90
Purchase #3	$179.57	9.265%	$196.2072	$196.21	$196.20	$196.20
Purchase #4	$224.79	3.656%	$233.0083	$233.01	$233.00	$233.00
Purchase #5	$198.46	3.756%	$205.9142	$205.91	$205.90	$205.90
Purchase #6	$66.61	11.230%	$74.0903	$74.09	$74.10	$74.10
Purchase #7	$123.53	4.211%	$128.7318	$128.73	$128.75	$128.70
7 purchase totals =	$994.54		$1,061.5006	$1,061.50	$1,061.50	$1,061.40