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	$118.40	13.666%	$134.5805	$134.58	$134.60	$134.60
Purchase #2	$126.66	13.199%	$143.3779	$143.38	$143.40	$143.40
Purchase #3	$24.93	11.121%	$27.7025	$27.70	$27.70	$27.70
Purchase #4	$28.90	13.339%	$32.755	$32.76	$32.75	$32.80
Purchase #5	$108.81	9.330%	$118.962	$118.96	$118.95	$119.00
Purchase #6	$155.26	5.719%	$164.1393	$164.14	$164.15	$164.10
Purchase #7	$72.61	13.588%	$82.4762	$82.48	$82.50	$82.50
7 purchase totals =	$635.57		$703.9934	$704.00	$704.05	$704.10