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	$76.70	11.509%	$85.5274	$85.53	$85.55	$85.50
Purchase #2	$56.90	4.724%	$59.588	$59.59	$59.60	$59.60
Purchase #3	$12.85	13.166%	$14.5418	$14.54	$14.55	$14.50
Purchase #4	$120.53	9.102%	$131.5006	$131.50	$131.50	$131.50
Purchase #5	$203.74	5.135%	$214.202	$214.20	$214.20	$214.20
Purchase #6	$110.95	6.673%	$118.3537	$118.35	$118.35	$118.40
Purchase #7	$81.62	6.185%	$86.6682	$86.67	$86.65	$86.70
7 purchase totals =	$663.29		$710.3817	$710.38	$710.40	$710.40