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	$222.84	8.857%	$242.5769	$242.58	$242.60	$242.60
Purchase #2	$61.68	6.152%	$65.4746	$65.47	$65.45	$65.50
Purchase #3	$201.25	11.105%	$223.5988	$223.60	$223.60	$223.60
Purchase #4	$46.42	11.771%	$51.8841	$51.88	$51.90	$51.90
Purchase #5	$142.88	4.143%	$148.7995	$148.80	$148.80	$148.80
Purchase #6	$171.36	9.820%	$188.1876	$188.19	$188.20	$188.20
Purchase #7	$22.88	6.650%	$24.4015	$24.40	$24.40	$24.40
7 purchase totals =	$869.31		$944.9230	$944.92	$944.95	$945.00