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	$62.39	8.230%	$67.5247	$67.52	$67.50	$67.50
Purchase #2	$218.26	6.760%	$233.0144	$233.01	$233.00	$233.00
Purchase #3	$21.51	6.262%	$22.857	$22.86	$22.85	$22.90
Purchase #4	$166.31	10.682%	$184.0752	$184.08	$184.10	$184.10
Purchase #5	$179.43	3.598%	$185.8859	$185.89	$185.90	$185.90
Purchase #6	$75.79	3.724%	$78.6124	$78.61	$78.60	$78.60
Purchase #7	$91.36	5.794%	$96.6534	$96.65	$96.65	$96.70
7 purchase totals =	$815.05		$868.6230	$868.62	$868.60	$868.70