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	$43.96	7.810%	$47.3933	$47.39	$47.40	$47.40
Purchase #2	$57.83	6.580%	$61.6352	$61.64	$61.65	$61.60
Purchase #3	$6.50	6.102%	$6.8966	$6.90	$6.90	$6.90
Purchase #4	$151.67	8.784%	$164.9927	$164.99	$165.00	$165.00
Purchase #5	$29.59	8.683%	$32.1593	$32.16	$32.15	$32.20
Purchase #6	$81.34	11.702%	$90.8584	$90.86	$90.85	$90.90
Purchase #7	$153.64	3.546%	$159.0881	$159.09	$159.10	$159.10
7 purchase totals =	$524.53		$563.0236	$563.03	$563.05	$563.10