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	$92.55	7.846%	$99.8115	$99.81	$99.80	$99.80
Purchase #2	$105.96	6.621%	$112.9756	$112.98	$113.00	$113.00
Purchase #3	$177.89	5.522%	$187.7131	$187.71	$187.70	$187.70
Purchase #4	$160.84	7.260%	$172.517	$172.52	$172.50	$172.50
Purchase #5	$46.27	10.242%	$51.009	$51.01	$51.00	$51.00
Purchase #6	$183.42	12.547%	$206.4337	$206.43	$206.45	$206.40
Purchase #7	$40.52	13.309%	$45.9128	$45.91	$45.90	$45.90
7 purchase totals =	$807.45		$876.3727	$876.37	$876.35	$876.30