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	$106.96	6.858%	$114.2953	$114.30	$114.30	$114.30
Purchase #2	$190.63	7.372%	$204.6832	$204.68	$204.70	$204.70
Purchase #3	$166.38	4.379%	$173.6658	$173.67	$173.65	$173.70
Purchase #4	$108.37	11.177%	$120.4825	$120.48	$120.50	$120.50
Purchase #5	$106.59	5.556%	$112.5121	$112.51	$112.50	$112.50
Purchase #6	$242.96	5.193%	$255.5769	$255.58	$255.60	$255.60
Purchase #7	$34.36	8.444%	$37.2614	$37.26	$37.25	$37.30
7 purchase totals =	$956.25		$1,018.4772	$1,018.48	$1,018.50	$1,018.60