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	$91.37	10.396%	$100.8688	$100.87	$100.85	$100.90
Purchase #2	$136.84	7.491%	$147.0907	$147.09	$147.10	$147.10
Purchase #3	$54.84	6.266%	$58.2763	$58.28	$58.30	$58.30
Purchase #4	$180.68	6.624%	$192.6482	$192.65	$192.65	$192.60
Purchase #5	$189.52	13.173%	$214.4855	$214.49	$214.50	$214.50
Purchase #6	$95.60	4.699%	$100.0922	$100.09	$100.10	$100.10
Purchase #7	$142.89	6.595%	$152.3136	$152.31	$152.30	$152.30
7 purchase totals =	$891.74		$965.7753	$965.78	$965.80	$965.80