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	$226.25	10.186%	$249.2958	$249.30	$249.30	$249.30
Purchase #2	$112.67	6.559%	$120.06	$120.06	$120.05	$120.10
Purchase #3	$161.43	11.335%	$179.7281	$179.73	$179.75	$179.70
Purchase #4	$52.47	13.215%	$59.4039	$59.40	$59.40	$59.40
Purchase #5	$242.98	5.188%	$255.5858	$255.59	$255.60	$255.60
Purchase #6	$102.86	13.381%	$116.6237	$116.62	$116.60	$116.60
Purchase #7	$214.94	8.357%	$232.9025	$232.90	$232.90	$232.90
7 purchase totals =	$1,113.60		$1,213.5998	$1,213.60	$1,213.60	$1,213.60