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	$123.29	6.766%	$131.6318	$131.63	$131.65	$131.60
Purchase #2	$216.95	7.264%	$232.7092	$232.71	$232.70	$232.70
Purchase #3	$62.94	13.764%	$71.6031	$71.60	$71.60	$71.60
Purchase #4	$127.70	8.525%	$138.5864	$138.59	$138.60	$138.60
Purchase #5	$163.78	5.127%	$172.177	$172.18	$172.20	$172.20
Purchase #6	$70.66	11.146%	$78.5358	$78.54	$78.55	$78.50
Purchase #7	$232.31	8.190%	$251.3362	$251.34	$251.35	$251.30
7 purchase totals =	$997.63		$1,076.5795	$1,076.59	$1,076.65	$1,076.50