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	$66.95	3.752%	$69.462	$69.46	$69.45	$69.50
Purchase #2	$48.99	4.774%	$51.3288	$51.33	$51.35	$51.30
Purchase #3	$85.94	11.225%	$95.5868	$95.59	$95.60	$95.60
Purchase #4	$48.36	9.430%	$52.9203	$52.92	$52.90	$52.90
Purchase #5	$62.66	5.116%	$65.8657	$65.87	$65.85	$65.90
Purchase #6	$190.59	13.274%	$215.8889	$215.89	$215.90	$215.90
Purchase #7	$220.80	4.333%	$230.3673	$230.37	$230.35	$230.40
7 purchase totals =	$724.29		$781.4198	$781.43	$781.40	$781.50