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	$198.45	12.754%	$223.7603	$223.76	$223.75	$223.80
Purchase #2	$141.33	13.579%	$160.5212	$160.52	$160.50	$160.50
Purchase #3	$128.69	10.513%	$142.2192	$142.22	$142.20	$142.20
Purchase #4	$153.83	4.328%	$160.4878	$160.49	$160.50	$160.50
Purchase #5	$23.60	13.452%	$26.7747	$26.77	$26.75	$26.80
Purchase #6	$138.60	12.577%	$156.0317	$156.03	$156.05	$156.00
Purchase #7	$181.67	13.296%	$205.8248	$205.82	$205.80	$205.80
7 purchase totals =	$966.17		$1,075.6197	$1,075.61	$1,075.55	$1,075.60