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	$190.38	5.264%	$200.4016	$200.40	$200.40	$200.40
Purchase #2	$26.86	5.801%	$28.4181	$28.42	$28.40	$28.40
Purchase #3	$140.70	5.291%	$148.1444	$148.14	$148.15	$148.10
Purchase #4	$63.80	6.642%	$68.0376	$68.04	$68.05	$68.00
Purchase #5	$190.81	8.244%	$206.5404	$206.54	$206.55	$206.50
Purchase #6	$180.77	3.608%	$187.2922	$187.29	$187.30	$187.30
Purchase #7	$126.25	10.803%	$139.8888	$139.89	$139.90	$139.90
7 purchase totals =	$919.57		$978.7231	$978.72	$978.75	$978.60