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	$213.43	5.551%	$225.2775	$225.28	$225.30	$225.30
Purchase #2	$170.82	10.387%	$188.5631	$188.56	$188.55	$188.60
Purchase #3	$163.64	9.691%	$179.4984	$179.50	$179.50	$179.50
Purchase #4	$136.70	11.647%	$152.6214	$152.62	$152.60	$152.60
Purchase #5	$151.93	8.364%	$164.6374	$164.64	$164.65	$164.60
Purchase #6	$69.42	10.214%	$76.5106	$76.51	$76.50	$76.50
Purchase #7	$151.51	4.853%	$158.8628	$158.86	$158.85	$158.90
7 purchase totals =	$1,057.45		$1,145.9712	$1,145.97	$1,145.95	$1,146.00