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	$56.70	8.630%	$61.5932	$61.59	$61.60	$61.60
Purchase #2	$78.98	10.740%	$87.4625	$87.46	$87.45	$87.50
Purchase #3	$131.37	10.146%	$144.6988	$144.70	$144.70	$144.70
Purchase #4	$184.70	5.225%	$194.3506	$194.35	$194.35	$194.40
Purchase #5	$82.42	9.317%	$90.0991	$90.10	$90.10	$90.10
Purchase #6	$14.74	7.855%	$15.8978	$15.90	$15.90	$15.90
Purchase #7	$121.26	13.702%	$137.875	$137.88	$137.90	$137.90
7 purchase totals =	$670.17		$731.9770	$731.98	$732.00	$732.10