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	$79.81	9.713%	$87.5619	$87.56	$87.55	$87.60
Purchase #2	$92.32	11.673%	$103.0965	$103.10	$103.10	$103.10
Purchase #3	$100.36	11.452%	$111.8532	$111.85	$111.85	$111.90
Purchase #4	$40.54	9.713%	$44.4777	$44.48	$44.50	$44.50
Purchase #5	$159.34	12.527%	$179.3005	$179.30	$179.30	$179.30
Purchase #6	$45.59	5.840%	$48.2525	$48.25	$48.25	$48.30
Purchase #7	$230.49	11.292%	$256.5169	$256.52	$256.50	$256.50
7 purchase totals =	$748.45		$831.0592	$831.06	$831.05	$831.20