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	$196.82	6.830%	$210.2628	$210.26	$210.25	$210.30
Purchase #2	$249.28	13.454%	$282.8181	$282.82	$282.80	$282.80
Purchase #3	$241.83	5.800%	$255.8561	$255.86	$255.85	$255.90
Purchase #4	$157.52	4.476%	$164.5706	$164.57	$164.55	$164.60
Purchase #5	$188.55	6.285%	$200.4004	$200.40	$200.40	$200.40
Purchase #6	$248.95	5.109%	$261.6689	$261.67	$261.65	$261.70
Purchase #7	$208.51	4.368%	$217.6177	$217.62	$217.60	$217.60
7 purchase totals =	$1,491.46		$1,593.1946	$1,593.20	$1,593.10	$1,593.30