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	$161.32	9.446%	$176.5583	$176.56	$176.55	$176.60
Purchase #2	$98.82	13.252%	$111.9156	$111.92	$111.90	$111.90
Purchase #3	$37.91	8.141%	$40.9963	$41.00	$41.00	$41.00
Purchase #4	$67.31	6.380%	$71.6044	$71.60	$71.60	$71.60
Purchase #5	$5.84	5.619%	$6.1681	$6.17	$6.15	$6.20
Purchase #6	$164.36	7.408%	$176.5358	$176.54	$176.55	$176.50
Purchase #7	$226.26	3.627%	$234.4665	$234.47	$234.45	$234.50
7 purchase totals =	$761.82		$818.2450	$818.26	$818.20	$818.30