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	$112.60	9.724%	$123.5492	$123.55	$123.55	$123.50
Purchase #2	$122.27	7.342%	$131.2471	$131.25	$131.25	$131.20
Purchase #3	$127.29	5.462%	$134.2426	$134.24	$134.25	$134.20
Purchase #4	$143.77	13.730%	$163.5096	$163.51	$163.50	$163.50
Purchase #5	$6.55	9.453%	$7.1692	$7.17	$7.15	$7.20
Purchase #6	$54.48	5.488%	$57.4699	$57.47	$57.45	$57.50
Purchase #7	$42.59	9.286%	$46.5449	$46.54	$46.55	$46.50
7 purchase totals =	$609.55		$663.7325	$663.73	$663.70	$663.60