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	$208.85	8.345%	$226.2785	$226.28	$226.30	$226.30
Purchase #2	$195.76	13.683%	$222.5458	$222.55	$222.55	$222.50
Purchase #3	$183.98	13.808%	$209.384	$209.38	$209.40	$209.40
Purchase #4	$52.67	7.277%	$56.5028	$56.50	$56.50	$56.50
Purchase #5	$47.51	11.570%	$53.0069	$53.01	$53.00	$53.00
Purchase #6	$5.28	3.450%	$5.4622	$5.46	$5.45	$5.50
Purchase #7	$248.45	9.723%	$272.6068	$272.61	$272.60	$272.60
7 purchase totals =	$942.50		$1,045.7870	$1,045.79	$1,045.80	$1,045.80