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	$123.67	7.126%	$132.4827	$132.48	$132.50	$132.50
Purchase #2	$196.35	10.772%	$217.5008	$217.50	$217.50	$217.50
Purchase #3	$109.49	3.300%	$113.1032	$113.10	$113.10	$113.10
Purchase #4	$63.42	13.861%	$72.2106	$72.21	$72.20	$72.20
Purchase #5	$217.43	10.181%	$239.5665	$239.57	$239.55	$239.60
Purchase #6	$160.45	4.749%	$168.0698	$168.07	$168.05	$168.10
Purchase #7	$89.42	11.248%	$99.478	$99.48	$99.50	$99.50
7 purchase totals =	$960.23		$1,042.4116	$1,042.41	$1,042.40	$1,042.50