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	$72.45	7.849%	$78.1366	$78.14	$78.15	$78.10
Purchase #2	$66.96	8.371%	$72.5652	$72.57	$72.55	$72.60
Purchase #3	$48.93	13.597%	$55.583	$55.58	$55.60	$55.60
Purchase #4	$72.67	9.602%	$79.6478	$79.65	$79.65	$79.60
Purchase #5	$64.59	9.117%	$70.4787	$70.48	$70.50	$70.50
Purchase #6	$46.95	12.119%	$52.6399	$52.64	$52.65	$52.60
Purchase #7	$72.63	12.172%	$81.4705	$81.47	$81.45	$81.50
7 purchase totals =	$445.18		$490.5217	$490.53	$490.55	$490.50