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	$77.81	5.300%	$81.9339	$81.93	$81.95	$81.90
Purchase #2	$62.93	5.468%	$66.371	$66.37	$66.35	$66.40
Purchase #3	$25.67	6.516%	$27.3427	$27.34	$27.35	$27.30
Purchase #4	$61.32	10.215%	$67.5838	$67.58	$67.60	$67.60
Purchase #5	$196.79	8.157%	$212.8422	$212.84	$212.85	$212.80
Purchase #6	$112.55	13.625%	$127.8849	$127.88	$127.90	$127.90
Purchase #7	$11.84	10.545%	$13.0885	$13.09	$13.10	$13.10
7 purchase totals =	$548.91		$597.0470	$597.03	$597.10	$597.00