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	$201.96	8.713%	$219.5568	$219.56	$219.55	$219.60
Purchase #2	$54.52	9.619%	$59.7643	$59.76	$59.75	$59.80
Purchase #3	$110.38	3.440%	$114.1771	$114.18	$114.20	$114.20
Purchase #4	$99.90	10.725%	$110.6143	$110.61	$110.60	$110.60
Purchase #5	$142.38	13.141%	$161.0902	$161.09	$161.10	$161.10
Purchase #6	$81.85	10.576%	$90.5065	$90.51	$90.50	$90.50
Purchase #7	$122.38	3.273%	$126.3855	$126.39	$126.40	$126.40
7 purchase totals =	$813.37		$882.0947	$882.10	$882.10	$882.20