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	$31.90	6.575%	$33.9974	$34.00	$34.00	$34.00
Purchase #2	$53.70	11.432%	$59.839	$59.84	$59.85	$59.80
Purchase #3	$143.65	12.810%	$162.0516	$162.05	$162.05	$162.10
Purchase #4	$211.36	6.732%	$225.5888	$225.59	$225.60	$225.60
Purchase #5	$214.95	9.437%	$235.2348	$235.23	$235.25	$235.20
Purchase #6	$29.35	10.665%	$32.4802	$32.48	$32.50	$32.50
Purchase #7	$50.38	5.340%	$53.0703	$53.07	$53.05	$53.10
7 purchase totals =	$735.29		$802.2621	$802.26	$802.30	$802.30