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	$50.69	5.712%	$53.5854	$53.59	$53.60	$53.60
Purchase #2	$165.26	13.203%	$187.0793	$187.08	$187.10	$187.10
Purchase #3	$227.57	10.667%	$251.8449	$251.84	$251.85	$251.80
Purchase #4	$71.92	11.270%	$80.0254	$80.03	$80.05	$80.00
Purchase #5	$93.86	7.421%	$100.8254	$100.83	$100.85	$100.80
Purchase #6	$233.66	12.389%	$262.6081	$262.61	$262.60	$262.60
Purchase #7	$95.42	10.653%	$105.5851	$105.59	$105.60	$105.60
7 purchase totals =	$938.38		$1,041.5536	$1,041.57	$1,041.65	$1,041.50