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	$37.75	10.313%	$41.6432	$41.64	$41.65	$41.60
Purchase #2	$132.50	6.618%	$141.2689	$141.27	$141.25	$141.30
Purchase #3	$171.95	11.667%	$192.0114	$192.01	$192.00	$192.00
Purchase #4	$136.84	11.531%	$152.619	$152.62	$152.60	$152.60
Purchase #5	$226.38	13.243%	$256.3595	$256.36	$256.35	$256.40
Purchase #6	$192.64	13.226%	$218.1186	$218.12	$218.10	$218.10
Purchase #7	$163.91	8.314%	$177.5375	$177.54	$177.55	$177.50
7 purchase totals =	$1,061.97		$1,179.5581	$1,179.56	$1,179.50	$1,179.50