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	$65.60	8.289%	$71.0376	$71.04	$71.05	$71.00
Purchase #2	$162.35	12.536%	$182.7022	$182.70	$182.70	$182.70
Purchase #3	$161.25	13.123%	$182.4108	$182.41	$182.40	$182.40
Purchase #4	$38.48	13.848%	$43.8087	$43.81	$43.80	$43.80
Purchase #5	$108.68	13.324%	$123.1605	$123.16	$123.15	$123.20
Purchase #6	$200.92	8.819%	$218.6391	$218.64	$218.65	$218.60
Purchase #7	$228.82	6.835%	$244.4598	$244.46	$244.45	$244.50
7 purchase totals =	$966.10		$1,066.2187	$1,066.22	$1,066.20	$1,066.20