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	$140.81	9.706%	$154.477	$154.48	$154.50	$154.50
Purchase #2	$93.28	7.353%	$100.1389	$100.14	$100.15	$100.10
Purchase #3	$86.43	10.541%	$95.5406	$95.54	$95.55	$95.50
Purchase #4	$126.26	3.350%	$130.4897	$130.49	$130.50	$130.50
Purchase #5	$23.47	4.491%	$24.524	$24.52	$24.50	$24.50
Purchase #6	$39.92	8.192%	$43.1902	$43.19	$43.20	$43.20
Purchase #7	$14.42	3.225%	$14.885	$14.89	$14.90	$14.90
7 purchase totals =	$524.59		$563.2454	$563.25	$563.30	$563.20