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	$164.65	12.146%	$184.6484	$184.65	$184.65	$184.60
Purchase #2	$63.33	13.136%	$71.649	$71.65	$71.65	$71.60
Purchase #3	$50.76	4.393%	$52.9899	$52.99	$53.00	$53.00
Purchase #4	$108.50	4.466%	$113.3456	$113.35	$113.35	$113.30
Purchase #5	$203.69	12.222%	$228.585	$228.59	$228.60	$228.60
Purchase #6	$108.27	7.615%	$116.5148	$116.51	$116.50	$116.50
Purchase #7	$107.67	5.204%	$113.2731	$113.27	$113.25	$113.30
7 purchase totals =	$806.87		$881.0058	$881.01	$881.00	$880.90