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	$137.48	9.113%	$150.0086	$150.01	$150.00	$150.00
Purchase #2	$103.55	5.190%	$108.9242	$108.92	$108.90	$108.90
Purchase #3	$30.43	11.202%	$33.8388	$33.84	$33.85	$33.80
Purchase #4	$26.36	4.684%	$27.5947	$27.59	$27.60	$27.60
Purchase #5	$112.39	10.751%	$124.473	$124.47	$124.45	$124.50
Purchase #6	$60.77	5.209%	$63.9355	$63.94	$63.95	$63.90
Purchase #7	$112.65	5.290%	$118.6092	$118.61	$118.60	$118.60
7 purchase totals =	$583.63		$627.3840	$627.38	$627.35	$627.30