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	$63.59	6.399%	$67.6591	$67.66	$67.65	$67.70
Purchase #2	$150.69	10.551%	$166.5893	$166.59	$166.60	$166.60
Purchase #3	$29.96	4.539%	$31.3199	$31.32	$31.30	$31.30
Purchase #4	$226.80	5.140%	$238.4575	$238.46	$238.45	$238.50
Purchase #5	$62.88	10.462%	$69.4585	$69.46	$69.45	$69.50
Purchase #6	$12.34	11.569%	$13.7676	$13.77	$13.75	$13.80
Purchase #7	$25.57	13.370%	$28.9887	$28.99	$29.00	$29.00
7 purchase totals =	$571.83		$616.2406	$616.25	$616.20	$616.40