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	$60.32	7.591%	$64.8989	$64.90	$64.90	$64.90
Purchase #2	$62.27	13.226%	$70.5058	$70.51	$70.50	$70.50
Purchase #3	$21.95	10.125%	$24.1724	$24.17	$24.15	$24.20
Purchase #4	$172.57	11.484%	$192.3879	$192.39	$192.40	$192.40
Purchase #5	$141.61	4.838%	$148.4611	$148.46	$148.45	$148.50
Purchase #6	$234.99	9.316%	$256.8817	$256.88	$256.90	$256.90
Purchase #7	$103.86	5.182%	$109.242	$109.24	$109.25	$109.20
7 purchase totals =	$797.57		$866.5498	$866.55	$866.55	$866.60