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	$94.62	11.496%	$105.4975	$105.50	$105.50	$105.50
Purchase #2	$141.87	10.233%	$156.3876	$156.39	$156.40	$156.40
Purchase #3	$192.44	8.863%	$209.496	$209.50	$209.50	$209.50
Purchase #4	$81.27	9.676%	$89.1337	$89.13	$89.15	$89.10
Purchase #5	$241.86	12.716%	$272.6149	$272.61	$272.60	$272.60
Purchase #6	$104.70	6.524%	$111.5306	$111.53	$111.55	$111.50
Purchase #7	$157.54	3.756%	$163.4572	$163.46	$163.45	$163.50
7 purchase totals =	$1,014.30		$1,108.1175	$1,108.12	$1,108.15	$1,108.10