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	$94.75	11.342%	$105.4965	$105.50	$105.50	$105.50
Purchase #2	$168.97	5.256%	$177.8511	$177.85	$177.85	$177.90
Purchase #3	$34.25	13.476%	$38.8655	$38.87	$38.85	$38.90
Purchase #4	$98.54	12.770%	$111.1236	$111.12	$111.10	$111.10
Purchase #5	$161.41	12.356%	$181.3538	$181.35	$181.35	$181.40
Purchase #6	$127.96	9.774%	$140.4668	$140.47	$140.45	$140.50
Purchase #7	$178.25	9.200%	$194.649	$194.65	$194.65	$194.60
7 purchase totals =	$864.13		$949.8063	$949.81	$949.75	$949.90