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	$106.94	6.103%	$113.4665	$113.47	$113.45	$113.50
Purchase #2	$34.75	9.117%	$37.9182	$37.92	$37.90	$37.90
Purchase #3	$203.71	5.630%	$215.1789	$215.18	$215.20	$215.20
Purchase #4	$63.90	5.536%	$67.4375	$67.44	$67.45	$67.40
Purchase #5	$244.39	4.495%	$255.3753	$255.38	$255.40	$255.40
Purchase #6	$159.79	11.208%	$177.6993	$177.70	$177.70	$177.70
Purchase #7	$225.60	3.675%	$233.8908	$233.89	$233.90	$233.90
7 purchase totals =	$1,039.08		$1,100.9665	$1,100.98	$1,101.00	$1,101.00