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	$45.42	7.738%	$48.9346	$48.93	$48.95	$48.90
Purchase #2	$161.42	4.445%	$168.5951	$168.60	$168.60	$168.60
Purchase #3	$121.35	5.321%	$127.807	$127.81	$127.80	$127.80
Purchase #4	$91.71	13.752%	$104.322	$104.32	$104.30	$104.30
Purchase #5	$140.67	9.812%	$154.4725	$154.47	$154.45	$154.50
Purchase #6	$174.96	9.866%	$192.2216	$192.22	$192.20	$192.20
Purchase #7	$67.83	7.525%	$72.9342	$72.93	$72.95	$72.90
7 purchase totals =	$803.36		$869.2870	$869.28	$869.25	$869.20