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	$217.87	10.166%	$240.0187	$240.02	$240.00	$240.00
Purchase #2	$148.65	6.486%	$158.2914	$158.29	$158.30	$158.30
Purchase #3	$152.39	4.863%	$159.8007	$159.80	$159.80	$159.80
Purchase #4	$31.53	10.837%	$34.9469	$34.95	$34.95	$34.90
Purchase #5	$152.83	8.573%	$165.9321	$165.93	$165.95	$165.90
Purchase #6	$132.87	10.247%	$146.4852	$146.49	$146.50	$146.50
Purchase #7	$175.84	11.700%	$196.4133	$196.41	$196.40	$196.40
7 purchase totals =	$1,011.98		$1,101.8883	$1,101.89	$1,101.90	$1,101.80