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	$137.93	10.628%	$152.5892	$152.59	$152.60	$152.60
Purchase #2	$163.42	5.649%	$172.6516	$172.65	$172.65	$172.70
Purchase #3	$227.25	6.774%	$242.6439	$242.64	$242.65	$242.60
Purchase #4	$48.96	4.217%	$51.0246	$51.02	$51.00	$51.00
Purchase #5	$168.50	8.273%	$182.44	$182.44	$182.45	$182.40
Purchase #6	$72.68	10.729%	$80.4778	$80.48	$80.50	$80.50
Purchase #7	$250.74	10.312%	$276.5963	$276.60	$276.60	$276.60
7 purchase totals =	$1,069.48		$1,158.4234	$1,158.42	$1,158.45	$1,158.40