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	$131.83	3.521%	$136.4717	$136.47	$136.45	$136.50
Purchase #2	$241.74	12.838%	$272.7746	$272.77	$272.75	$272.80
Purchase #3	$123.93	8.193%	$134.0836	$134.08	$134.10	$134.10
Purchase #4	$57.92	6.127%	$61.4688	$61.47	$61.45	$61.50
Purchase #5	$161.68	10.608%	$178.831	$178.83	$178.85	$178.80
Purchase #6	$190.37	4.461%	$198.8624	$198.86	$198.85	$198.90
Purchase #7	$161.30	11.533%	$179.9027	$179.90	$179.90	$179.90
7 purchase totals =	$1,068.77		$1,162.3948	$1,162.38	$1,162.35	$1,162.50