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	$170.38	10.392%	$188.0859	$188.09	$188.10	$188.10
Purchase #2	$117.85	13.297%	$133.5205	$133.52	$133.50	$133.50
Purchase #3	$100.57	4.202%	$104.796	$104.80	$104.80	$104.80
Purchase #4	$35.34	9.128%	$38.5658	$38.57	$38.55	$38.60
Purchase #5	$196.88	12.558%	$221.6042	$221.60	$221.60	$221.60
Purchase #6	$91.42	3.865%	$94.9534	$94.95	$94.95	$95.00
Purchase #7	$216.78	8.572%	$235.3624	$235.36	$235.35	$235.40
7 purchase totals =	$929.22		$1,016.8882	$1,016.89	$1,016.85	$1,017.00