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	$247.93	3.487%	$256.5753	$256.58	$256.60	$256.60
Purchase #2	$95.81	5.403%	$100.9866	$100.99	$101.00	$101.00
Purchase #3	$42.29	5.524%	$44.6261	$44.63	$44.65	$44.60
Purchase #4	$38.60	4.233%	$40.2339	$40.23	$40.25	$40.20
Purchase #5	$101.61	12.777%	$114.5927	$114.59	$114.60	$114.60
Purchase #6	$189.33	5.846%	$200.3982	$200.40	$200.40	$200.40
Purchase #7	$63.85	7.430%	$68.5941	$68.59	$68.60	$68.60
7 purchase totals =	$779.42		$826.0069	$826.01	$826.10	$826.00