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	$109.60	4.392%	$114.4136	$114.41	$114.40	$114.40
Purchase #2	$182.60	6.381%	$194.2517	$194.25	$194.25	$194.30
Purchase #3	$157.27	9.508%	$172.2232	$172.22	$172.20	$172.20
Purchase #4	$166.89	11.434%	$185.9722	$185.97	$185.95	$186.00
Purchase #5	$229.65	3.301%	$237.2307	$237.23	$237.25	$237.20
Purchase #6	$176.62	11.807%	$197.4735	$197.47	$197.45	$197.50
Purchase #7	$69.64	12.585%	$78.4042	$78.40	$78.40	$78.40
7 purchase totals =	$1,092.27		$1,179.9691	$1,179.95	$1,179.90	$1,180.00