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	$61.80	9.429%	$67.6271	$67.63	$67.65	$67.60
Purchase #2	$63.42	12.868%	$71.5809	$71.58	$71.60	$71.60
Purchase #3	$153.40	7.380%	$164.7209	$164.72	$164.70	$164.70
Purchase #4	$188.72	11.243%	$209.9378	$209.94	$209.95	$209.90
Purchase #5	$111.90	6.144%	$118.7751	$118.78	$118.80	$118.80
Purchase #6	$224.39	7.432%	$241.0667	$241.07	$241.05	$241.10
Purchase #7	$185.59	12.354%	$208.5178	$208.52	$208.50	$208.50
7 purchase totals =	$989.22		$1,082.2263	$1,082.24	$1,082.25	$1,082.20