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	$99.41	12.526%	$111.8621	$111.86	$111.85	$111.90
Purchase #2	$69.86	3.639%	$72.4022	$72.40	$72.40	$72.40
Purchase #3	$171.63	9.686%	$188.2541	$188.25	$188.25	$188.30
Purchase #4	$51.39	4.858%	$53.8865	$53.89	$53.90	$53.90
Purchase #5	$198.64	10.326%	$219.1516	$219.15	$219.15	$219.20
Purchase #6	$163.97	7.430%	$176.153	$176.15	$176.15	$176.20
Purchase #7	$250.81	10.159%	$276.2898	$276.29	$276.30	$276.30
7 purchase totals =	$1,005.71		$1,097.9993	$1,097.99	$1,098.00	$1,098.20