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	$99.90	11.379%	$111.2676	$111.27	$111.25	$111.30
Purchase #2	$18.53	12.257%	$20.8012	$20.80	$20.80	$20.80
Purchase #3	$126.59	9.614%	$138.7604	$138.76	$138.75	$138.80
Purchase #4	$16.67	9.774%	$18.2993	$18.30	$18.30	$18.30
Purchase #5	$22.60	7.843%	$24.3725	$24.37	$24.35	$24.40
Purchase #6	$225.40	3.116%	$232.4235	$232.42	$232.40	$232.40
Purchase #7	$245.83	3.756%	$255.0634	$255.06	$255.05	$255.10
7 purchase totals =	$755.52		$800.9879	$800.98	$800.90	$801.10