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	$108.83	7.582%	$117.0815	$117.08	$117.10	$117.10
Purchase #2	$138.75	9.342%	$151.712	$151.71	$151.70	$151.70
Purchase #3	$175.71	13.610%	$199.6241	$199.62	$199.60	$199.60
Purchase #4	$153.67	9.569%	$168.3747	$168.37	$168.35	$168.40
Purchase #5	$157.30	4.490%	$164.3628	$164.36	$164.35	$164.40
Purchase #6	$83.93	5.443%	$88.4983	$88.50	$88.50	$88.50
Purchase #7	$114.80	7.848%	$123.8095	$123.81	$123.80	$123.80
7 purchase totals =	$932.99		$1,013.4629	$1,013.45	$1,013.40	$1,013.50