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	$56.26	11.619%	$62.7968	$62.80	$62.80	$62.80
Purchase #2	$104.68	8.712%	$113.7997	$113.80	$113.80	$113.80
Purchase #3	$103.82	7.767%	$111.8837	$111.88	$111.90	$111.90
Purchase #4	$192.41	11.368%	$214.2832	$214.28	$214.30	$214.30
Purchase #5	$22.86	6.155%	$24.267	$24.27	$24.25	$24.30
Purchase #6	$214.30	4.729%	$224.4342	$224.43	$224.45	$224.40
Purchase #7	$52.68	12.596%	$59.3156	$59.32	$59.30	$59.30
7 purchase totals =	$747.01		$810.7802	$810.78	$810.80	$810.80