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	$121.38	4.302%	$126.6018	$126.60	$126.60	$126.60
Purchase #2	$127.70	12.739%	$143.9677	$143.97	$143.95	$144.00
Purchase #3	$137.58	12.682%	$155.0279	$155.03	$155.05	$155.00
Purchase #4	$148.91	13.221%	$168.5974	$168.60	$168.60	$168.60
Purchase #5	$240.52	6.185%	$255.3962	$255.40	$255.40	$255.40
Purchase #6	$164.47	13.316%	$186.3708	$186.37	$186.35	$186.40
Purchase #7	$38.53	7.653%	$41.4787	$41.48	$41.50	$41.50
7 purchase totals =	$979.09		$1,077.4405	$1,077.45	$1,077.45	$1,077.50