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	$146.60	5.677%	$154.9225	$154.92	$154.90	$154.90
Purchase #2	$227.65	12.732%	$256.6344	$256.63	$256.65	$256.60
Purchase #3	$11.91	5.128%	$12.5207	$12.52	$12.50	$12.50
Purchase #4	$171.72	5.762%	$181.6145	$181.61	$181.60	$181.60
Purchase #5	$101.97	11.156%	$113.3458	$113.35	$113.35	$113.30
Purchase #6	$96.66	13.455%	$109.6656	$109.67	$109.65	$109.70
Purchase #7	$30.52	5.833%	$32.3002	$32.30	$32.30	$32.30
7 purchase totals =	$787.03		$861.0037	$861.00	$860.95	$860.90