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	$129.65	5.221%	$136.419	$136.42	$136.40	$136.40
Purchase #2	$16.67	5.569%	$17.5984	$17.60	$17.60	$17.60
Purchase #3	$118.95	6.265%	$126.4022	$126.40	$126.40	$126.40
Purchase #4	$153.77	12.244%	$172.5976	$172.60	$172.60	$172.60
Purchase #5	$81.61	13.384%	$92.5327	$92.53	$92.55	$92.50
Purchase #6	$163.33	5.874%	$172.924	$172.92	$172.90	$172.90
Purchase #7	$135.35	11.488%	$150.899	$150.90	$150.90	$150.90
7 purchase totals =	$799.33		$869.3729	$869.37	$869.35	$869.30