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	$39.58	4.697%	$41.4391	$41.44	$41.45	$41.40
Purchase #2	$43.97	3.551%	$45.5314	$45.53	$45.55	$45.50
Purchase #3	$150.93	12.351%	$169.5714	$169.57	$169.55	$169.60
Purchase #4	$114.85	8.670%	$124.8075	$124.81	$124.80	$124.80
Purchase #5	$89.99	10.535%	$99.4704	$99.47	$99.45	$99.50
Purchase #6	$57.25	10.348%	$63.1742	$63.17	$63.15	$63.20
Purchase #7	$157.99	13.606%	$179.4861	$179.49	$179.50	$179.50
7 purchase totals =	$654.56		$723.4801	$723.48	$723.45	$723.50