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	$180.32	8.834%	$196.2495	$196.25	$196.25	$196.20
Purchase #2	$63.59	11.732%	$71.0504	$71.05	$71.05	$71.10
Purchase #3	$206.93	4.160%	$215.5383	$215.54	$215.55	$215.50
Purchase #4	$172.99	3.417%	$178.9011	$178.90	$178.90	$178.90
Purchase #5	$138.58	4.380%	$144.6498	$144.65	$144.65	$144.60
Purchase #6	$203.36	12.615%	$229.0139	$229.01	$229.00	$229.00
Purchase #7	$230.67	8.642%	$250.6045	$250.60	$250.60	$250.60
7 purchase totals =	$1,196.44		$1,286.0075	$1,286.00	$1,286.00	$1,285.90