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	$245.57	9.789%	$269.6088	$269.61	$269.60	$269.60
Purchase #2	$46.50	11.408%	$51.8047	$51.80	$51.80	$51.80
Purchase #3	$238.35	8.777%	$259.27	$259.27	$259.25	$259.30
Purchase #4	$80.84	7.158%	$86.6265	$86.63	$86.65	$86.60
Purchase #5	$202.32	9.706%	$221.9572	$221.96	$221.95	$222.00
Purchase #6	$176.62	6.602%	$188.2805	$188.28	$188.30	$188.30
Purchase #7	$65.57	11.136%	$72.8719	$72.87	$72.85	$72.90
7 purchase totals =	$1,055.77		$1,150.4196	$1,150.42	$1,150.40	$1,150.50