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	$241.34	13.812%	$274.6739	$274.67	$274.65	$274.70
Purchase #2	$225.88	6.509%	$240.5825	$240.58	$240.60	$240.60
Purchase #3	$169.34	6.275%	$179.9661	$179.97	$179.95	$180.00
Purchase #4	$205.90	13.504%	$233.7047	$233.70	$233.70	$233.70
Purchase #5	$217.75	11.308%	$242.3732	$242.37	$242.35	$242.40
Purchase #6	$89.59	3.403%	$92.6387	$92.64	$92.65	$92.60
Purchase #7	$74.45	5.723%	$78.7108	$78.71	$78.70	$78.70
7 purchase totals =	$1,224.25		$1,342.6499	$1,342.64	$1,342.60	$1,342.70