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	$131.66	11.246%	$146.4665	$146.47	$146.45	$146.50
Purchase #2	$141.65	8.661%	$153.9183	$153.92	$153.90	$153.90
Purchase #3	$77.48	10.699%	$85.7696	$85.77	$85.75	$85.80
Purchase #4	$129.78	10.231%	$143.0578	$143.06	$143.05	$143.10
Purchase #5	$123.30	6.392%	$131.1813	$131.18	$131.20	$131.20
Purchase #6	$71.66	13.449%	$81.2976	$81.30	$81.30	$81.30
Purchase #7	$41.71	9.102%	$45.5064	$45.51	$45.50	$45.50
7 purchase totals =	$717.24		$787.1975	$787.21	$787.15	$787.30