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	$128.94	11.630%	$143.9357	$143.94	$143.95	$143.90
Purchase #2	$116.84	8.339%	$126.5833	$126.58	$126.60	$126.60
Purchase #3	$177.83	9.346%	$194.45	$194.45	$194.45	$194.50
Purchase #4	$203.61	8.121%	$220.1452	$220.15	$220.15	$220.10
Purchase #5	$220.77	12.673%	$248.7482	$248.75	$248.75	$248.70
Purchase #6	$29.85	6.647%	$31.8341	$31.83	$31.85	$31.80
Purchase #7	$80.31	11.458%	$89.5119	$89.51	$89.50	$89.50
7 purchase totals =	$958.15		$1,055.2084	$1,055.21	$1,055.25	$1,055.10