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	$213.82	7.517%	$229.8928	$229.89	$229.90	$229.90
Purchase #2	$61.32	13.371%	$69.5191	$69.52	$69.50	$69.50
Purchase #3	$190.82	11.136%	$212.0697	$212.07	$212.05	$212.10
Purchase #4	$217.25	13.503%	$246.5853	$246.59	$246.60	$246.60
Purchase #5	$157.98	11.723%	$176.5	$176.50	$176.50	$176.50
Purchase #6	$131.33	8.806%	$142.8949	$142.89	$142.90	$142.90
Purchase #7	$169.47	12.713%	$191.0147	$191.01	$191.00	$191.00
7 purchase totals =	$1,141.99		$1,268.4765	$1,268.47	$1,268.45	$1,268.50