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	$213.41	9.557%	$233.8056	$233.81	$233.80	$233.80
Purchase #2	$87.31	5.873%	$92.4377	$92.44	$92.45	$92.40
Purchase #3	$225.78	8.572%	$245.1339	$245.13	$245.15	$245.10
Purchase #4	$195.51	13.773%	$222.4376	$222.44	$222.45	$222.40
Purchase #5	$16.41	13.295%	$18.5917	$18.59	$18.60	$18.60
Purchase #6	$10.54	9.208%	$11.5105	$11.51	$11.50	$11.50
Purchase #7	$130.97	11.461%	$145.9805	$145.98	$146.00	$146.00
7 purchase totals =	$879.93		$969.8975	$969.90	$969.95	$969.80