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	$208.56	10.497%	$230.4525	$230.45	$230.45	$230.50
Purchase #2	$182.25	10.365%	$201.1402	$201.14	$201.15	$201.10
Purchase #3	$73.70	6.538%	$78.5185	$78.52	$78.50	$78.50
Purchase #4	$53.51	6.611%	$57.0475	$57.05	$57.05	$57.00
Purchase #5	$92.61	12.844%	$104.5048	$104.50	$104.50	$104.50
Purchase #6	$87.69	4.431%	$91.5755	$91.58	$91.60	$91.60
Purchase #7	$91.36	9.800%	$100.3133	$100.31	$100.30	$100.30
7 purchase totals =	$789.68		$863.5523	$863.55	$863.55	$863.50