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	$188.94	6.167%	$200.5919	$200.59	$200.60	$200.60
Purchase #2	$81.48	9.250%	$89.0169	$89.02	$89.00	$89.00
Purchase #3	$153.40	12.716%	$172.9063	$172.91	$172.90	$172.90
Purchase #4	$170.35	7.649%	$183.3801	$183.38	$183.40	$183.40
Purchase #5	$47.42	10.624%	$52.4579	$52.46	$52.45	$52.50
Purchase #6	$224.29	5.384%	$236.3658	$236.37	$236.35	$236.40
Purchase #7	$108.87	12.156%	$122.1042	$122.10	$122.10	$122.10
7 purchase totals =	$974.75		$1,056.8231	$1,056.83	$1,056.80	$1,056.90