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	$146.87	7.491%	$157.872	$157.87	$157.85	$157.90
Purchase #2	$245.29	7.596%	$263.9222	$263.92	$263.90	$263.90
Purchase #3	$144.96	12.186%	$162.6248	$162.62	$162.60	$162.60
Purchase #4	$93.64	12.642%	$105.478	$105.48	$105.50	$105.50
Purchase #5	$242.77	5.565%	$256.2802	$256.28	$256.30	$256.30
Purchase #6	$233.42	11.352%	$259.9178	$259.92	$259.90	$259.90
Purchase #7	$89.90	3.273%	$92.8424	$92.84	$92.85	$92.80
7 purchase totals =	$1,196.85		$1,298.9374	$1,298.93	$1,298.90	$1,298.90