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	$100.36	5.444%	$105.8236	$105.82	$105.80	$105.80
Purchase #2	$192.92	9.816%	$211.857	$211.86	$211.85	$211.90
Purchase #3	$104.52	8.772%	$113.6885	$113.69	$113.70	$113.70
Purchase #4	$171.29	7.188%	$183.6023	$183.60	$183.60	$183.60
Purchase #5	$184.47	8.575%	$200.2883	$200.29	$200.30	$200.30
Purchase #6	$126.48	7.868%	$136.4314	$136.43	$136.45	$136.40
Purchase #7	$25.59	3.225%	$26.4153	$26.42	$26.40	$26.40
7 purchase totals =	$905.63		$978.1064	$978.11	$978.10	$978.10