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	$146.82	5.254%	$154.5339	$154.53	$154.55	$154.50
Purchase #2	$170.85	6.634%	$182.1842	$182.18	$182.20	$182.20
Purchase #3	$194.78	10.312%	$214.8657	$214.87	$214.85	$214.90
Purchase #4	$98.84	12.310%	$111.0072	$111.01	$111.00	$111.00
Purchase #5	$124.41	13.535%	$141.2489	$141.25	$141.25	$141.20
Purchase #6	$136.54	10.484%	$150.8549	$150.85	$150.85	$150.90
Purchase #7	$123.65	8.749%	$134.4681	$134.47	$134.45	$134.50
7 purchase totals =	$995.89		$1,089.1629	$1,089.16	$1,089.15	$1,089.20