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	$205.97	3.674%	$213.5373	$213.54	$213.55	$213.50
Purchase #2	$98.92	5.658%	$104.5169	$104.52	$104.50	$104.50
Purchase #3	$239.59	11.366%	$266.8218	$266.82	$266.80	$266.80
Purchase #4	$104.71	6.488%	$111.5036	$111.50	$111.50	$111.50
Purchase #5	$119.60	5.833%	$126.5763	$126.58	$126.60	$126.60
Purchase #6	$70.43	13.288%	$79.7887	$79.79	$79.80	$79.80
Purchase #7	$154.97	6.137%	$164.4805	$164.48	$164.50	$164.50
7 purchase totals =	$994.19		$1,067.2251	$1,067.23	$1,067.25	$1,067.20