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	$204.72	11.181%	$227.6097	$227.61	$227.60	$227.60
Purchase #2	$52.35	13.750%	$59.5481	$59.55	$59.55	$59.50
Purchase #3	$52.73	13.728%	$59.9688	$59.97	$59.95	$60.00
Purchase #4	$60.86	5.507%	$64.2116	$64.21	$64.20	$64.20
Purchase #5	$103.97	6.828%	$111.0691	$111.07	$111.05	$111.10
Purchase #6	$162.93	3.338%	$168.3686	$168.37	$168.35	$168.40
Purchase #7	$211.97	12.170%	$237.7667	$237.77	$237.75	$237.80
7 purchase totals =	$849.53		$928.5426	$928.55	$928.45	$928.60