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	$30.74	6.754%	$32.8162	$32.82	$32.80	$32.80
Purchase #2	$192.26	3.700%	$199.3736	$199.37	$199.35	$199.40
Purchase #3	$127.85	12.736%	$144.133	$144.13	$144.15	$144.10
Purchase #4	$50.55	11.825%	$56.5275	$56.53	$56.55	$56.50
Purchase #5	$230.25	13.272%	$260.8088	$260.81	$260.80	$260.80
Purchase #6	$179.77	9.831%	$197.4432	$197.44	$197.45	$197.40
Purchase #7	$167.50	10.144%	$184.4912	$184.49	$184.50	$184.50
7 purchase totals =	$978.92		$1,075.5935	$1,075.59	$1,075.60	$1,075.50