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	$143.55	8.366%	$155.5594	$155.56	$155.55	$155.60
Purchase #2	$38.57	5.838%	$40.8217	$40.82	$40.80	$40.80
Purchase #3	$173.98	5.534%	$183.6081	$183.61	$183.60	$183.60
Purchase #4	$196.89	7.835%	$212.3163	$212.32	$212.30	$212.30
Purchase #5	$123.72	11.704%	$138.2002	$138.20	$138.20	$138.20
Purchase #6	$193.78	6.289%	$205.9668	$205.97	$205.95	$206.00
Purchase #7	$119.90	6.635%	$127.8554	$127.86	$127.85	$127.90
7 purchase totals =	$990.39		$1,064.3279	$1,064.34	$1,064.25	$1,064.40