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	$84.94	8.765%	$92.385	$92.39	$92.40	$92.40
Purchase #2	$217.69	3.177%	$224.606	$224.61	$224.60	$224.60
Purchase #3	$82.75	8.403%	$89.7035	$89.70	$89.70	$89.70
Purchase #4	$11.66	13.617%	$13.2477	$13.25	$13.25	$13.20
Purchase #5	$159.68	12.314%	$179.343	$179.34	$179.35	$179.30
Purchase #6	$20.91	7.551%	$22.4889	$22.49	$22.50	$22.50
Purchase #7	$72.85	7.371%	$78.2198	$78.22	$78.20	$78.20
7 purchase totals =	$650.48		$699.9939	$700.00	$700.00	$699.90