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	$31.90	5.418%	$33.6283	$33.63	$33.65	$33.60
Purchase #2	$151.66	4.532%	$158.5332	$158.53	$158.55	$158.50
Purchase #3	$60.67	6.293%	$64.488	$64.49	$64.50	$64.50
Purchase #4	$51.61	4.656%	$54.013	$54.01	$54.00	$54.00
Purchase #5	$237.76	9.588%	$260.5564	$260.56	$260.55	$260.60
Purchase #6	$103.65	12.326%	$116.4259	$116.43	$116.45	$116.40
Purchase #7	$216.56	13.487%	$245.7674	$245.77	$245.75	$245.80
7 purchase totals =	$853.81		$933.4122	$933.42	$933.45	$933.40