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	$218.82	10.397%	$241.5707	$241.57	$241.55	$241.60
Purchase #2	$57.27	9.607%	$62.7719	$62.77	$62.75	$62.80
Purchase #3	$62.76	3.191%	$64.7627	$64.76	$64.75	$64.80
Purchase #4	$133.65	12.513%	$150.3736	$150.37	$150.35	$150.40
Purchase #5	$93.28	5.615%	$98.5177	$98.52	$98.50	$98.50
Purchase #6	$226.28	5.129%	$237.8859	$237.89	$237.90	$237.90
Purchase #7	$114.26	8.170%	$123.595	$123.60	$123.60	$123.60
7 purchase totals =	$906.32		$979.4775	$979.48	$979.40	$979.60