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	$97.67	8.368%	$105.843	$105.84	$105.85	$105.80
Purchase #2	$18.37	8.128%	$19.8631	$19.86	$19.85	$19.90
Purchase #3	$115.85	9.547%	$126.9102	$126.91	$126.90	$126.90
Purchase #4	$28.42	10.334%	$31.3569	$31.36	$31.35	$31.40
Purchase #5	$82.42	11.624%	$92.0005	$92.00	$92.00	$92.00
Purchase #6	$129.91	13.254%	$147.1283	$147.13	$147.15	$147.10
Purchase #7	$128.51	12.429%	$144.4825	$144.48	$144.50	$144.50
7 purchase totals =	$601.15		$667.5845	$667.58	$667.60	$667.60