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	$193.80	3.448%	$200.4822	$200.48	$200.50	$200.50
Purchase #2	$136.47	6.858%	$145.8291	$145.83	$145.85	$145.80
Purchase #3	$106.73	3.197%	$110.1422	$110.14	$110.15	$110.10
Purchase #4	$24.86	11.536%	$27.7278	$27.73	$27.75	$27.70
Purchase #5	$67.82	4.458%	$70.8434	$70.84	$70.85	$70.80
Purchase #6	$38.76	13.273%	$43.9046	$43.90	$43.90	$43.90
Purchase #7	$132.39	10.293%	$146.0169	$146.02	$146.00	$146.00
7 purchase totals =	$700.83		$744.9462	$744.94	$745.00	$744.80