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	$212.43	5.841%	$224.838	$224.84	$224.85	$224.80
Purchase #2	$51.91	12.341%	$58.3162	$58.32	$58.30	$58.30
Purchase #3	$153.41	5.771%	$162.2633	$162.26	$162.25	$162.30
Purchase #4	$58.83	3.833%	$61.085	$61.09	$61.10	$61.10
Purchase #5	$88.50	4.485%	$92.4692	$92.47	$92.45	$92.50
Purchase #6	$137.37	3.695%	$142.4458	$142.45	$142.45	$142.40
Purchase #7	$97.61	10.218%	$107.5838	$107.58	$107.60	$107.60
7 purchase totals =	$800.06		$849.0013	$849.01	$849.00	$849.00