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	$164.40	7.351%	$176.485	$176.49	$176.50	$176.50
Purchase #2	$135.87	11.112%	$150.9679	$150.97	$150.95	$151.00
Purchase #3	$179.34	6.116%	$190.3084	$190.31	$190.30	$190.30
Purchase #4	$184.30	4.303%	$192.2304	$192.23	$192.25	$192.20
Purchase #5	$36.76	7.340%	$39.4582	$39.46	$39.45	$39.50
Purchase #6	$145.28	5.635%	$153.4665	$153.47	$153.45	$153.50
Purchase #7	$100.86	13.442%	$114.4176	$114.42	$114.40	$114.40
7 purchase totals =	$946.81		$1,017.3340	$1,017.35	$1,017.30	$1,017.40