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	$127.46	4.708%	$133.4608	$133.46	$133.45	$133.50
Purchase #2	$67.26	3.649%	$69.7143	$69.71	$69.70	$69.70
Purchase #3	$147.60	6.859%	$157.7239	$157.72	$157.70	$157.70
Purchase #4	$137.54	4.587%	$143.849	$143.85	$143.85	$143.80
Purchase #5	$69.82	3.210%	$72.0612	$72.06	$72.05	$72.10
Purchase #6	$51.45	4.276%	$53.65	$53.65	$53.65	$53.70
Purchase #7	$101.91	9.368%	$111.4569	$111.46	$111.45	$111.50
7 purchase totals =	$703.04		$741.9161	$741.91	$741.85	$742.00