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	$151.81	8.401%	$164.5636	$164.56	$164.55	$164.60
Purchase #2	$166.79	3.269%	$172.2424	$172.24	$172.25	$172.20
Purchase #3	$206.47	4.357%	$215.4659	$215.47	$215.45	$215.50
Purchase #4	$127.88	10.112%	$140.8112	$140.81	$140.80	$140.80
Purchase #5	$217.50	8.395%	$235.7591	$235.76	$235.75	$235.80
Purchase #6	$178.45	8.162%	$193.0151	$193.02	$193.00	$193.00
Purchase #7	$41.60	4.757%	$43.5789	$43.58	$43.60	$43.60
7 purchase totals =	$1,090.50		$1,165.4362	$1,165.44	$1,165.40	$1,165.50