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	$223.71	3.469%	$231.4705	$231.47	$231.45	$231.50
Purchase #2	$139.52	9.134%	$152.2638	$152.26	$152.25	$152.30
Purchase #3	$219.56	6.325%	$233.4472	$233.45	$233.45	$233.40
Purchase #4	$95.79	9.482%	$104.8728	$104.87	$104.85	$104.90
Purchase #5	$138.91	9.845%	$152.5857	$152.59	$152.60	$152.60
Purchase #6	$249.28	6.295%	$264.9722	$264.97	$264.95	$265.00
Purchase #7	$58.66	5.577%	$61.9315	$61.93	$61.95	$61.90
7 purchase totals =	$1,125.43		$1,201.5437	$1,201.54	$1,201.50	$1,201.60