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	$179.39	4.710%	$187.8393	$187.84	$187.85	$187.80
Purchase #2	$88.25	4.393%	$92.1268	$92.13	$92.15	$92.10
Purchase #3	$86.43	7.523%	$92.9321	$92.93	$92.95	$92.90
Purchase #4	$100.43	3.214%	$103.6578	$103.66	$103.65	$103.70
Purchase #5	$120.47	4.493%	$125.8827	$125.88	$125.90	$125.90
Purchase #6	$159.84	3.628%	$165.639	$165.64	$165.65	$165.60
Purchase #7	$121.69	8.139%	$131.5943	$131.59	$131.60	$131.60
7 purchase totals =	$856.50		$899.6720	$899.67	$899.75	$899.60