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	$27.27	5.474%	$28.7628	$28.76	$28.75	$28.80
Purchase #2	$79.60	13.806%	$90.5896	$90.59	$90.60	$90.60
Purchase #3	$95.26	5.189%	$100.203	$100.20	$100.20	$100.20
Purchase #4	$143.85	5.614%	$151.9257	$151.93	$151.95	$151.90
Purchase #5	$179.98	10.714%	$199.2631	$199.26	$199.25	$199.30
Purchase #6	$172.74	3.452%	$178.703	$178.70	$178.70	$178.70
Purchase #7	$132.28	5.423%	$139.4535	$139.45	$139.45	$139.50
7 purchase totals =	$830.98		$888.9007	$888.89	$888.90	$889.00