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	$134.87	10.167%	$148.5822	$148.58	$148.60	$148.60
Purchase #2	$157.64	10.742%	$174.5737	$174.57	$174.55	$174.60
Purchase #3	$58.31	11.515%	$65.0244	$65.02	$65.00	$65.00
Purchase #4	$40.50	6.226%	$43.0215	$43.02	$43.00	$43.00
Purchase #5	$127.61	11.320%	$142.0555	$142.06	$142.05	$142.10
Purchase #6	$55.86	9.742%	$61.3019	$61.30	$61.30	$61.30
Purchase #7	$143.43	5.863%	$151.8393	$151.84	$151.85	$151.80
7 purchase totals =	$718.22		$786.3985	$786.39	$786.35	$786.40