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	$163.59	12.103%	$183.3893	$183.39	$183.40	$183.40
Purchase #2	$143.67	3.209%	$148.2804	$148.28	$148.30	$148.30
Purchase #3	$79.40	8.116%	$85.8441	$85.84	$85.85	$85.80
Purchase #4	$81.87	10.194%	$90.2158	$90.22	$90.20	$90.20
Purchase #5	$169.94	9.718%	$186.4548	$186.45	$186.45	$186.50
Purchase #6	$219.68	11.169%	$244.2161	$244.22	$244.20	$244.20
Purchase #7	$232.56	3.846%	$241.5043	$241.50	$241.50	$241.50
7 purchase totals =	$1,090.71		$1,179.9048	$1,179.90	$1,179.90	$1,179.90