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	$70.79	11.490%	$78.9238	$78.92	$78.90	$78.90
Purchase #2	$171.85	3.161%	$177.2822	$177.28	$177.30	$177.30
Purchase #3	$163.65	4.828%	$171.551	$171.55	$171.55	$171.60
Purchase #4	$219.69	5.277%	$231.283	$231.28	$231.30	$231.30
Purchase #5	$38.49	6.139%	$40.8529	$40.85	$40.85	$40.90
Purchase #6	$168.93	10.246%	$186.2386	$186.24	$186.25	$186.20
Purchase #7	$206.37	6.178%	$219.1195	$219.12	$219.10	$219.10
7 purchase totals =	$1,039.77		$1,105.2510	$1,105.24	$1,105.25	$1,105.30