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	$146.92	4.671%	$153.7826	$153.78	$153.80	$153.80
Purchase #2	$41.69	8.475%	$45.2232	$45.22	$45.20	$45.20
Purchase #3	$155.49	8.484%	$168.6818	$168.68	$168.70	$168.70
Purchase #4	$219.98	6.136%	$233.478	$233.48	$233.50	$233.50
Purchase #5	$174.42	3.851%	$181.1369	$181.14	$181.15	$181.10
Purchase #6	$79.29	12.523%	$89.2195	$89.22	$89.20	$89.20
Purchase #7	$49.38	5.224%	$51.9596	$51.96	$51.95	$52.00
7 purchase totals =	$867.17		$923.4816	$923.48	$923.50	$923.50