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	$218.33	11.690%	$243.8528	$243.85	$243.85	$243.90
Purchase #2	$91.35	9.826%	$100.3261	$100.33	$100.35	$100.30
Purchase #3	$226.68	9.202%	$247.5391	$247.54	$247.55	$247.50
Purchase #4	$60.67	7.266%	$65.0783	$65.08	$65.10	$65.10
Purchase #5	$143.30	3.845%	$148.8099	$148.81	$148.80	$148.80
Purchase #6	$88.78	12.683%	$100.04	$100.04	$100.05	$100.00
Purchase #7	$83.70	10.688%	$92.6459	$92.65	$92.65	$92.60
7 purchase totals =	$912.81		$998.2921	$998.30	$998.35	$998.20