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	$58.42	7.590%	$62.8541	$62.85	$62.85	$62.90
Purchase #2	$39.65	7.526%	$42.6341	$42.63	$42.65	$42.60
Purchase #3	$108.55	5.631%	$114.6625	$114.66	$114.65	$114.70
Purchase #4	$51.54	9.634%	$56.5054	$56.51	$56.50	$56.50
Purchase #5	$74.82	9.540%	$81.9578	$81.96	$81.95	$82.00
Purchase #6	$158.38	5.373%	$166.8898	$166.89	$166.90	$166.90
Purchase #7	$23.61	4.151%	$24.5901	$24.59	$24.60	$24.60
7 purchase totals =	$514.97		$550.0938	$550.09	$550.10	$550.20