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	$21.45	5.553%	$22.6411	$22.64	$22.65	$22.60
Purchase #2	$40.70	10.125%	$44.8209	$44.82	$44.80	$44.80
Purchase #3	$84.60	6.722%	$90.2868	$90.29	$90.30	$90.30
Purchase #4	$100.93	12.805%	$113.8541	$113.85	$113.85	$113.90
Purchase #5	$99.43	5.359%	$104.7585	$104.76	$104.75	$104.80
Purchase #6	$77.93	3.472%	$80.6357	$80.64	$80.65	$80.60
Purchase #7	$227.68	4.712%	$238.4083	$238.41	$238.40	$238.40
7 purchase totals =	$652.72		$695.4054	$695.41	$695.40	$695.40