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	$214.84	9.531%	$235.3164	$235.32	$235.30	$235.30
Purchase #2	$96.89	12.505%	$109.0061	$109.01	$109.00	$109.00
Purchase #3	$185.89	6.751%	$198.4394	$198.44	$198.45	$198.40
Purchase #4	$164.54	5.139%	$172.9957	$173.00	$173.00	$173.00
Purchase #5	$118.25	11.351%	$131.6726	$131.67	$131.65	$131.70
Purchase #6	$81.42	10.619%	$90.066	$90.07	$90.05	$90.10
Purchase #7	$211.80	7.248%	$227.1513	$227.15	$227.15	$227.20
7 purchase totals =	$1,073.63		$1,164.6475	$1,164.66	$1,164.60	$1,164.70