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	$13.52	6.324%	$14.375	$14.38	$14.40	$14.40
Purchase #2	$212.72	8.340%	$230.4608	$230.46	$230.45	$230.50
Purchase #3	$173.98	4.839%	$182.3989	$182.40	$182.40	$182.40
Purchase #4	$60.88	9.861%	$66.8834	$66.88	$66.90	$66.90
Purchase #5	$33.43	10.865%	$37.0622	$37.06	$37.05	$37.10
Purchase #6	$153.37	7.162%	$164.3544	$164.35	$164.35	$164.40
Purchase #7	$76.83	7.184%	$82.3495	$82.35	$82.35	$82.30
7 purchase totals =	$724.73		$777.8842	$777.88	$777.90	$778.00