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	$53.62	10.171%	$59.0737	$59.07	$59.05	$59.10
Purchase #2	$150.47	7.249%	$161.3776	$161.38	$161.40	$161.40
Purchase #3	$155.32	13.524%	$176.3255	$176.33	$176.35	$176.30
Purchase #4	$148.78	3.853%	$154.5125	$154.51	$154.50	$154.50
Purchase #5	$138.64	10.661%	$153.4204	$153.42	$153.40	$153.40
Purchase #6	$90.94	3.716%	$94.3193	$94.32	$94.30	$94.30
Purchase #7	$29.82	5.857%	$31.5666	$31.57	$31.55	$31.60
7 purchase totals =	$767.59		$830.5956	$830.60	$830.55	$830.60