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	$40.92	8.285%	$44.3102	$44.31	$44.30	$44.30
Purchase #2	$167.96	10.545%	$185.6714	$185.67	$185.65	$185.70
Purchase #3	$137.26	12.616%	$154.5767	$154.58	$154.60	$154.60
Purchase #4	$177.64	10.387%	$196.0915	$196.09	$196.10	$196.10
Purchase #5	$81.72	5.873%	$86.5194	$86.52	$86.50	$86.50
Purchase #6	$60.48	8.271%	$65.4823	$65.48	$65.50	$65.50
Purchase #7	$223.42	6.333%	$237.5692	$237.57	$237.55	$237.60
7 purchase totals =	$889.40		$970.2207	$970.22	$970.20	$970.30