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	$54.25	12.465%	$61.0123	$61.01	$61.00	$61.00
Purchase #2	$183.45	13.530%	$208.2708	$208.27	$208.25	$208.30
Purchase #3	$133.64	9.340%	$146.122	$146.12	$146.10	$146.10
Purchase #4	$31.53	12.523%	$35.4785	$35.48	$35.50	$35.50
Purchase #5	$105.28	6.212%	$111.82	$111.82	$111.80	$111.80
Purchase #6	$157.25	12.864%	$177.4786	$177.48	$177.50	$177.50
Purchase #7	$168.29	5.438%	$177.4416	$177.44	$177.45	$177.40
7 purchase totals =	$833.69		$917.6238	$917.62	$917.60	$917.60