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	$136.39	8.844%	$148.4523	$148.45	$148.45	$148.50
Purchase #2	$87.98	13.462%	$99.8239	$99.82	$99.80	$99.80
Purchase #3	$23.94	8.256%	$25.9165	$25.92	$25.90	$25.90
Purchase #4	$218.79	13.811%	$249.0071	$249.01	$249.00	$249.00
Purchase #5	$239.71	9.560%	$262.6263	$262.63	$262.65	$262.60
Purchase #6	$107.35	10.437%	$118.5541	$118.55	$118.55	$118.60
Purchase #7	$154.64	11.607%	$172.5891	$172.59	$172.60	$172.60
7 purchase totals =	$968.80		$1,076.9693	$1,076.97	$1,076.95	$1,077.00