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	$171.51	5.199%	$180.4268	$180.43	$180.45	$180.40
Purchase #2	$160.70	11.480%	$179.1484	$179.15	$179.15	$179.10
Purchase #3	$116.52	5.199%	$122.5779	$122.58	$122.60	$122.60
Purchase #4	$18.52	8.495%	$20.0933	$20.09	$20.10	$20.10
Purchase #5	$148.78	3.139%	$153.4502	$153.45	$153.45	$153.50
Purchase #6	$73.55	5.852%	$77.8541	$77.85	$77.85	$77.90
Purchase #7	$248.42	8.645%	$269.8959	$269.90	$269.90	$269.90
7 purchase totals =	$938.00		$1,003.4466	$1,003.45	$1,003.50	$1,003.50