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	$153.30	7.149%	$164.2594	$164.26	$164.25	$164.30
Purchase #2	$90.81	9.398%	$99.3443	$99.34	$99.35	$99.30
Purchase #3	$101.91	9.691%	$111.7861	$111.79	$111.80	$111.80
Purchase #4	$161.32	10.745%	$178.6538	$178.65	$178.65	$178.70
Purchase #5	$192.42	3.544%	$199.2394	$199.24	$199.25	$199.20
Purchase #6	$233.89	10.773%	$259.087	$259.09	$259.10	$259.10
Purchase #7	$133.55	9.421%	$146.1317	$146.13	$146.15	$146.10
7 purchase totals =	$1,067.20		$1,158.5017	$1,158.50	$1,158.55	$1,158.50