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	$115.92	6.777%	$123.7759	$123.78	$123.80	$123.80
Purchase #2	$164.51	7.848%	$177.4207	$177.42	$177.40	$177.40
Purchase #3	$83.57	4.829%	$87.6056	$87.61	$87.60	$87.60
Purchase #4	$104.34	6.868%	$111.5061	$111.51	$111.50	$111.50
Purchase #5	$185.29	10.568%	$204.8714	$204.87	$204.85	$204.90
Purchase #6	$115.59	6.739%	$123.3796	$123.38	$123.40	$123.40
Purchase #7	$193.97	11.290%	$215.8692	$215.87	$215.85	$215.90
7 purchase totals =	$963.19		$1,044.4285	$1,044.44	$1,044.40	$1,044.50