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	$102.53	8.874%	$111.6285	$111.63	$111.65	$111.60
Purchase #2	$232.43	9.516%	$254.548	$254.55	$254.55	$254.50
Purchase #3	$115.59	7.651%	$124.4338	$124.43	$124.45	$124.40
Purchase #4	$155.45	7.724%	$167.457	$167.46	$167.45	$167.50
Purchase #5	$247.76	12.862%	$279.6269	$279.63	$279.65	$279.60
Purchase #6	$217.75	7.414%	$233.894	$233.89	$233.90	$233.90
Purchase #7	$78.30	12.318%	$87.945	$87.95	$87.95	$87.90
7 purchase totals =	$1,149.81		$1,259.5332	$1,259.54	$1,259.60	$1,259.40