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	$212.37	13.810%	$241.6983	$241.70	$241.70	$241.70
Purchase #2	$72.94	8.133%	$78.8722	$78.87	$78.85	$78.90
Purchase #3	$12.32	10.789%	$13.6492	$13.65	$13.65	$13.60
Purchase #4	$215.43	8.762%	$234.306	$234.31	$234.30	$234.30
Purchase #5	$203.86	6.730%	$217.5798	$217.58	$217.60	$217.60
Purchase #6	$94.26	7.863%	$101.6717	$101.67	$101.65	$101.70
Purchase #7	$175.45	11.815%	$196.1794	$196.18	$196.20	$196.20
7 purchase totals =	$986.63		$1,083.9566	$1,083.96	$1,083.95	$1,084.00