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	$32.45	7.505%	$34.8854	$34.89	$34.90	$34.90
Purchase #2	$65.82	9.510%	$72.0795	$72.08	$72.10	$72.10
Purchase #3	$40.58	8.316%	$43.9546	$43.95	$43.95	$44.00
Purchase #4	$158.47	7.340%	$170.1017	$170.10	$170.10	$170.10
Purchase #5	$228.78	11.250%	$254.5178	$254.52	$254.50	$254.50
Purchase #6	$175.93	13.169%	$199.0982	$199.10	$199.10	$199.10
Purchase #7	$19.88	11.121%	$22.0909	$22.09	$22.10	$22.10
7 purchase totals =	$721.91		$796.7281	$796.73	$796.75	$796.80