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	$111.98	4.125%	$116.5992	$116.60	$116.60	$116.60
Purchase #2	$103.81	12.237%	$116.5132	$116.51	$116.50	$116.50
Purchase #3	$87.38	5.118%	$91.8521	$91.85	$91.85	$91.90
Purchase #4	$18.95	6.169%	$20.119	$20.12	$20.10	$20.10
Purchase #5	$143.83	8.602%	$156.2023	$156.20	$156.20	$156.20
Purchase #6	$150.83	9.764%	$165.557	$165.56	$165.55	$165.60
Purchase #7	$51.99	7.664%	$55.9745	$55.97	$55.95	$56.00
7 purchase totals =	$668.77		$722.8173	$722.81	$722.75	$722.90