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	$210.34	3.863%	$218.4654	$218.47	$218.45	$218.50
Purchase #2	$48.88	12.258%	$54.8717	$54.87	$54.85	$54.90
Purchase #3	$207.89	10.718%	$230.1717	$230.17	$230.15	$230.20
Purchase #4	$239.53	8.293%	$259.3942	$259.39	$259.40	$259.40
Purchase #5	$155.81	12.273%	$174.9326	$174.93	$174.95	$174.90
Purchase #6	$10.32	12.295%	$11.5888	$11.59	$11.60	$11.60
Purchase #7	$173.27	3.576%	$179.4661	$179.47	$179.45	$179.50
7 purchase totals =	$1,046.04		$1,128.8905	$1,128.89	$1,128.85	$1,129.00