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	$208.55	4.658%	$218.2643	$218.26	$218.25	$218.30
Purchase #2	$56.57	7.699%	$60.9253	$60.93	$60.95	$60.90
Purchase #3	$90.60	5.793%	$95.8485	$95.85	$95.85	$95.80
Purchase #4	$27.78	12.186%	$31.1653	$31.17	$31.15	$31.20
Purchase #5	$93.54	7.467%	$100.5246	$100.52	$100.50	$100.50
Purchase #6	$41.53	7.712%	$44.7328	$44.73	$44.75	$44.70
Purchase #7	$151.70	9.769%	$166.5196	$166.52	$166.50	$166.50
7 purchase totals =	$670.27		$717.9804	$717.98	$717.95	$717.90