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	$188.51	10.829%	$208.9237	$208.92	$208.90	$208.90
Purchase #2	$67.32	8.128%	$72.7918	$72.79	$72.80	$72.80
Purchase #3	$58.53	6.773%	$62.4942	$62.49	$62.50	$62.50
Purchase #4	$164.94	5.169%	$173.4657	$173.47	$173.45	$173.50
Purchase #5	$244.75	13.325%	$277.3629	$277.36	$277.35	$277.40
Purchase #6	$54.32	5.114%	$57.0979	$57.10	$57.10	$57.10
Purchase #7	$237.40	3.762%	$246.331	$246.33	$246.35	$246.30
7 purchase totals =	$1,015.77		$1,098.4672	$1,098.46	$1,098.45	$1,098.50