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	$191.82	8.659%	$208.4297	$208.43	$208.45	$208.40
Purchase #2	$180.25	5.793%	$190.6919	$190.69	$190.70	$190.70
Purchase #3	$214.51	12.373%	$241.0513	$241.05	$241.05	$241.10
Purchase #4	$23.46	8.261%	$25.398	$25.40	$25.40	$25.40
Purchase #5	$48.98	4.614%	$51.2399	$51.24	$51.25	$51.20
Purchase #6	$134.72	5.740%	$142.4529	$142.45	$142.45	$142.50
Purchase #7	$46.67	4.127%	$48.5961	$48.60	$48.60	$48.60
7 purchase totals =	$840.41		$907.8598	$907.86	$907.90	$907.90