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	$43.89	5.604%	$46.3496	$46.35	$46.35	$46.30
Purchase #2	$56.93	3.319%	$58.8195	$58.82	$58.80	$58.80
Purchase #3	$91.47	9.850%	$100.4798	$100.48	$100.50	$100.50
Purchase #4	$145.37	8.738%	$158.0724	$158.07	$158.05	$158.10
Purchase #5	$179.83	6.774%	$192.0117	$192.01	$192.00	$192.00
Purchase #6	$14.49	6.737%	$15.4662	$15.47	$15.45	$15.50
Purchase #7	$126.29	8.282%	$136.7493	$136.75	$136.75	$136.70
7 purchase totals =	$658.27		$707.9485	$707.95	$707.90	$707.90