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	$64.88	4.633%	$67.8859	$67.89	$67.90	$67.90
Purchase #2	$52.57	12.423%	$59.1008	$59.10	$59.10	$59.10
Purchase #3	$178.46	7.547%	$191.9284	$191.93	$191.95	$191.90
Purchase #4	$36.99	7.519%	$39.7713	$39.77	$39.75	$39.80
Purchase #5	$145.59	5.397%	$153.4475	$153.45	$153.45	$153.40
Purchase #6	$43.32	9.660%	$47.5047	$47.50	$47.50	$47.50
Purchase #7	$159.54	8.716%	$173.4455	$173.45	$173.45	$173.40
7 purchase totals =	$681.35		$733.0841	$733.09	$733.10	$733.00