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	$74.83	3.509%	$77.4558	$77.46	$77.45	$77.50
Purchase #2	$97.46	8.376%	$105.6232	$105.62	$105.60	$105.60
Purchase #3	$216.75	6.728%	$231.3329	$231.33	$231.35	$231.30
Purchase #4	$33.97	10.120%	$37.4078	$37.41	$37.40	$37.40
Purchase #5	$109.43	12.841%	$123.4819	$123.48	$123.50	$123.50
Purchase #6	$94.71	6.648%	$101.0063	$101.01	$101.00	$101.00
Purchase #7	$146.47	3.400%	$151.45	$151.45	$151.45	$151.50
7 purchase totals =	$773.62		$827.7579	$827.76	$827.75	$827.80