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	$67.69	12.163%	$75.9231	$75.92	$75.90	$75.90
Purchase #2	$108.42	10.225%	$119.5059	$119.51	$119.50	$119.50
Purchase #3	$117.25	5.360%	$123.5346	$123.53	$123.55	$123.50
Purchase #4	$196.96	4.569%	$205.9591	$205.96	$205.95	$206.00
Purchase #5	$193.53	7.594%	$208.2267	$208.23	$208.25	$208.20
Purchase #6	$82.77	3.233%	$85.446	$85.45	$85.45	$85.40
Purchase #7	$67.50	10.194%	$74.381	$74.38	$74.40	$74.40
7 purchase totals =	$834.12		$892.9764	$892.98	$893.00	$892.90