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	$54.92	3.650%	$56.9246	$56.92	$56.90	$56.90
Purchase #2	$69.86	10.306%	$77.0598	$77.06	$77.05	$77.10
Purchase #3	$142.69	8.392%	$154.6645	$154.66	$154.65	$154.70
Purchase #4	$32.59	5.873%	$34.504	$34.50	$34.50	$34.50
Purchase #5	$107.55	5.512%	$113.4782	$113.48	$113.50	$113.50
Purchase #6	$128.64	13.186%	$145.6025	$145.60	$145.60	$145.60
Purchase #7	$113.65	4.361%	$118.6063	$118.61	$118.60	$118.60
7 purchase totals =	$649.90		$700.8399	$700.83	$700.80	$700.90