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	$104.25	13.402%	$118.2216	$118.22	$118.20	$118.20
Purchase #2	$101.71	9.746%	$111.6227	$111.62	$111.60	$111.60
Purchase #3	$216.67	13.123%	$245.1036	$245.10	$245.10	$245.10
Purchase #4	$201.56	13.404%	$228.5771	$228.58	$228.60	$228.60
Purchase #5	$33.68	6.382%	$35.8295	$35.83	$35.85	$35.80
Purchase #6	$118.80	6.142%	$126.0967	$126.10	$126.10	$126.10
Purchase #7	$166.96	12.612%	$188.017	$188.02	$188.00	$188.00
7 purchase totals =	$943.63		$1,053.4682	$1,053.47	$1,053.45	$1,053.40