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	$224.40	13.131%	$253.866	$253.87	$253.85	$253.90
Purchase #2	$135.67	5.779%	$143.5104	$143.51	$143.50	$143.50
Purchase #3	$76.30	4.845%	$79.9967	$80.00	$80.00	$80.00
Purchase #4	$17.90	12.428%	$20.1246	$20.12	$20.10	$20.10
Purchase #5	$186.65	5.451%	$196.8243	$196.82	$196.80	$196.80
Purchase #6	$107.78	4.420%	$112.5439	$112.54	$112.55	$112.50
Purchase #7	$218.47	9.234%	$238.6435	$238.64	$238.65	$238.60
7 purchase totals =	$967.17		$1,045.5094	$1,045.50	$1,045.45	$1,045.40