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	$33.63	10.242%	$37.0744	$37.07	$37.05	$37.10
Purchase #2	$214.37	4.693%	$224.4304	$224.43	$224.45	$224.40
Purchase #3	$133.48	13.812%	$151.9163	$151.92	$151.90	$151.90
Purchase #4	$28.32	9.423%	$30.9886	$30.99	$31.00	$31.00
Purchase #5	$139.64	5.699%	$147.5981	$147.60	$147.60	$147.60
Purchase #6	$240.75	6.291%	$255.8956	$255.90	$255.90	$255.90
Purchase #7	$115.26	13.683%	$131.031	$131.03	$131.05	$131.00
7 purchase totals =	$905.45		$978.9344	$978.94	$978.95	$978.90