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	$237.27	13.421%	$269.114	$269.11	$269.10	$269.10
Purchase #2	$56.51	3.680%	$58.5896	$58.59	$58.60	$58.60
Purchase #3	$185.37	5.139%	$194.8962	$194.90	$194.90	$194.90
Purchase #4	$123.46	6.510%	$131.4972	$131.50	$131.50	$131.50
Purchase #5	$108.83	12.298%	$122.2139	$122.21	$122.20	$122.20
Purchase #6	$73.79	3.639%	$76.4752	$76.48	$76.50	$76.50
Purchase #7	$49.59	8.237%	$53.6747	$53.67	$53.65	$53.70
7 purchase totals =	$834.82		$906.4608	$906.46	$906.45	$906.50