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	$61.77	6.208%	$65.6047	$65.60	$65.60	$65.60
Purchase #2	$124.59	10.198%	$137.2957	$137.30	$137.30	$137.30
Purchase #3	$132.84	6.823%	$141.9037	$141.90	$141.90	$141.90
Purchase #4	$169.74	3.509%	$175.6962	$175.70	$175.70	$175.70
Purchase #5	$132.41	3.817%	$137.4641	$137.46	$137.45	$137.50
Purchase #6	$131.66	13.840%	$149.8817	$149.88	$149.90	$149.90
Purchase #7	$33.36	12.474%	$37.5213	$37.52	$37.50	$37.50
7 purchase totals =	$786.37		$845.3674	$845.36	$845.35	$845.40