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	$10.72	6.647%	$11.4326	$11.43	$11.45	$11.40
Purchase #2	$72.57	11.250%	$80.7341	$80.73	$80.75	$80.70
Purchase #3	$40.50	6.149%	$42.9903	$42.99	$43.00	$43.00
Purchase #4	$148.60	6.676%	$158.5205	$158.52	$158.50	$158.50
Purchase #5	$57.59	3.465%	$59.5855	$59.59	$59.60	$59.60
Purchase #6	$153.43	13.639%	$174.3563	$174.36	$174.35	$174.40
Purchase #7	$226.35	9.503%	$247.86	$247.86	$247.85	$247.90
7 purchase totals =	$709.76		$775.4793	$775.48	$775.50	$775.50