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	$206.51	5.855%	$218.6012	$218.60	$218.60	$218.60
Purchase #2	$157.29	5.699%	$166.254	$166.25	$166.25	$166.30
Purchase #3	$213.76	11.514%	$238.3723	$238.37	$238.35	$238.40
Purchase #4	$97.26	12.757%	$109.6675	$109.67	$109.65	$109.70
Purchase #5	$118.50	7.511%	$127.4005	$127.40	$127.40	$127.40
Purchase #6	$20.27	13.117%	$22.9288	$22.93	$22.95	$22.90
Purchase #7	$103.44	10.446%	$114.2453	$114.25	$114.25	$114.20
7 purchase totals =	$917.03		$997.4696	$997.47	$997.45	$997.50