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	$235.78	9.215%	$257.5071	$257.51	$257.50	$257.50
Purchase #2	$219.91	12.149%	$246.6269	$246.63	$246.65	$246.60
Purchase #3	$152.38	10.744%	$168.7517	$168.75	$168.75	$168.80
Purchase #4	$54.67	9.500%	$59.8637	$59.86	$59.85	$59.90
Purchase #5	$98.99	9.560%	$108.4534	$108.45	$108.45	$108.50
Purchase #6	$151.69	5.168%	$159.5293	$159.53	$159.55	$159.50
Purchase #7	$112.65	9.334%	$123.1648	$123.16	$123.15	$123.20
7 purchase totals =	$1,026.07		$1,123.8969	$1,123.89	$1,123.90	$1,124.00