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	$214.75	6.520%	$228.7517	$228.75	$228.75	$228.80
Purchase #2	$148.34	12.471%	$166.8395	$166.84	$166.85	$166.80
Purchase #3	$180.67	9.870%	$198.5021	$198.50	$198.50	$198.50
Purchase #4	$247.98	4.779%	$259.831	$259.83	$259.85	$259.80
Purchase #5	$137.59	13.789%	$156.5623	$156.56	$156.55	$156.60
Purchase #6	$99.80	13.832%	$113.6043	$113.60	$113.60	$113.60
Purchase #7	$221.31	5.423%	$233.3116	$233.31	$233.30	$233.30
7 purchase totals =	$1,250.44		$1,357.4025	$1,357.39	$1,357.40	$1,357.40