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	$117.81	12.398%	$132.4161	$132.42	$132.40	$132.40
Purchase #2	$156.53	6.424%	$166.5855	$166.59	$166.60	$166.60
Purchase #3	$157.26	4.446%	$164.2518	$164.25	$164.25	$164.30
Purchase #4	$33.81	3.168%	$34.8811	$34.88	$34.90	$34.90
Purchase #5	$100.51	4.834%	$105.3687	$105.37	$105.35	$105.40
Purchase #6	$90.67	10.533%	$100.2203	$100.22	$100.20	$100.20
Purchase #7	$46.45	9.772%	$50.9891	$50.99	$51.00	$51.00
7 purchase totals =	$703.04		$754.7126	$754.72	$754.70	$754.80