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	$103.58	7.540%	$111.3899	$111.39	$111.40	$111.40
Purchase #2	$199.50	3.711%	$206.9034	$206.90	$206.90	$206.90
Purchase #3	$117.72	12.567%	$132.5139	$132.51	$132.50	$132.50
Purchase #4	$245.30	5.799%	$259.5249	$259.52	$259.50	$259.50
Purchase #5	$144.56	10.731%	$160.0727	$160.07	$160.05	$160.10
Purchase #6	$86.85	13.182%	$98.2986	$98.30	$98.30	$98.30
Purchase #7	$115.97	4.849%	$121.5934	$121.59	$121.60	$121.60
7 purchase totals =	$1,013.48		$1,090.2968	$1,090.28	$1,090.25	$1,090.30