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	$14.30	6.440%	$15.2209	$15.22	$15.20	$15.20
Purchase #2	$220.96	4.448%	$230.7883	$230.79	$230.80	$230.80
Purchase #3	$80.27	9.179%	$87.638	$87.64	$87.65	$87.60
Purchase #4	$239.83	8.622%	$260.5081	$260.51	$260.50	$260.50
Purchase #5	$178.38	10.180%	$196.5391	$196.54	$196.55	$196.50
Purchase #6	$157.91	9.312%	$172.6146	$172.61	$172.60	$172.60
Purchase #7	$49.88	9.225%	$54.4814	$54.48	$54.50	$54.50
7 purchase totals =	$941.53		$1,017.7904	$1,017.79	$1,017.80	$1,017.70