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	$145.27	10.147%	$160.0105	$160.01	$160.00	$160.00
Purchase #2	$148.25	7.803%	$159.8179	$159.82	$159.80	$159.80
Purchase #3	$103.90	8.378%	$112.6047	$112.60	$112.60	$112.60
Purchase #4	$7.37	3.329%	$7.6153	$7.62	$7.60	$7.60
Purchase #5	$66.62	7.772%	$71.7977	$71.80	$71.80	$71.80
Purchase #6	$34.77	6.352%	$36.9786	$36.98	$37.00	$37.00
Purchase #7	$19.40	10.405%	$21.4186	$21.42	$21.40	$21.40
7 purchase totals =	$525.58		$570.2433	$570.25	$570.20	$570.20