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	$53.93	10.285%	$59.4767	$59.48	$59.50	$59.50
Purchase #2	$200.87	3.526%	$207.9527	$207.95	$207.95	$208.00
Purchase #3	$77.45	5.739%	$81.8949	$81.89	$81.90	$81.90
Purchase #4	$122.52	13.359%	$138.8874	$138.89	$138.90	$138.90
Purchase #5	$78.33	10.576%	$86.6142	$86.61	$86.60	$86.60
Purchase #6	$232.87	9.464%	$254.9088	$254.91	$254.90	$254.90
Purchase #7	$70.73	11.204%	$78.6546	$78.65	$78.65	$78.70
7 purchase totals =	$836.70		$908.3893	$908.38	$908.40	$908.50