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	$53.96	9.476%	$59.0732	$59.07	$59.05	$59.10
Purchase #2	$61.90	11.112%	$68.7783	$68.78	$68.80	$68.80
Purchase #3	$100.41	3.252%	$103.6753	$103.68	$103.70	$103.70
Purchase #4	$126.38	13.705%	$143.7004	$143.70	$143.70	$143.70
Purchase #5	$59.41	3.629%	$61.566	$61.57	$61.55	$61.60
Purchase #6	$228.33	3.750%	$236.8924	$236.89	$236.90	$236.90
Purchase #7	$231.30	10.164%	$254.8093	$254.81	$254.80	$254.80
7 purchase totals =	$861.69		$928.4949	$928.50	$928.50	$928.60