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	$48.47	10.295%	$53.46	$53.46	$53.45	$53.50
Purchase #2	$91.83	4.540%	$95.9991	$96.00	$96.00	$96.00
Purchase #3	$118.96	5.618%	$125.6432	$125.64	$125.65	$125.60
Purchase #4	$206.87	5.106%	$217.4328	$217.43	$217.45	$217.40
Purchase #5	$81.53	9.184%	$89.0177	$89.02	$89.00	$89.00
Purchase #6	$222.62	4.870%	$233.4616	$233.46	$233.45	$233.50
Purchase #7	$50.47	4.173%	$52.5761	$52.58	$52.60	$52.60
7 purchase totals =	$820.75		$867.5905	$867.59	$867.60	$867.60