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	$168.97	9.425%	$184.8954	$184.90	$184.90	$184.90
Purchase #2	$59.82	10.189%	$65.9151	$65.92	$65.90	$65.90
Purchase #3	$147.64	7.682%	$158.9817	$158.98	$159.00	$159.00
Purchase #4	$78.49	6.246%	$83.3925	$83.39	$83.40	$83.40
Purchase #5	$32.29	5.849%	$34.1786	$34.18	$34.20	$34.20
Purchase #6	$45.60	5.128%	$47.9384	$47.94	$47.95	$47.90
Purchase #7	$97.92	12.106%	$109.7742	$109.77	$109.75	$109.80
7 purchase totals =	$630.73		$685.0759	$685.08	$685.10	$685.10