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	$230.66	4.307%	$240.5945	$240.59	$240.60	$240.60
Purchase #2	$93.46	5.573%	$98.6685	$98.67	$98.65	$98.70
Purchase #3	$54.39	9.321%	$59.4597	$59.46	$59.45	$59.50
Purchase #4	$26.43	5.713%	$27.9399	$27.94	$27.95	$27.90
Purchase #5	$190.86	4.602%	$199.6434	$199.64	$199.65	$199.60
Purchase #6	$161.77	6.660%	$172.5439	$172.54	$172.55	$172.50
Purchase #7	$119.86	4.136%	$124.8174	$124.82	$124.80	$124.80
7 purchase totals =	$877.43		$923.6673	$923.66	$923.65	$923.60