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	$81.45	13.108%	$92.1265	$92.13	$92.15	$92.10
Purchase #2	$137.81	5.583%	$145.5039	$145.50	$145.50	$145.50
Purchase #3	$223.52	12.679%	$251.8601	$251.86	$251.85	$251.90
Purchase #4	$45.51	13.252%	$51.541	$51.54	$51.55	$51.50
Purchase #5	$58.34	8.594%	$63.3537	$63.35	$63.35	$63.40
Purchase #6	$127.41	12.781%	$143.6943	$143.69	$143.70	$143.70
Purchase #7	$182.91	5.458%	$192.8932	$192.89	$192.90	$192.90
7 purchase totals =	$856.95		$940.9727	$940.96	$941.00	$941.00