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	$118.32	8.513%	$128.3926	$128.39	$128.40	$128.40
Purchase #2	$72.28	11.380%	$80.5055	$80.51	$80.50	$80.50
Purchase #3	$150.98	5.237%	$158.8868	$158.89	$158.90	$158.90
Purchase #4	$55.49	11.209%	$61.7099	$61.71	$61.70	$61.70
Purchase #5	$142.75	3.412%	$147.6206	$147.62	$147.60	$147.60
Purchase #6	$192.93	12.197%	$216.4617	$216.46	$216.45	$216.50
Purchase #7	$212.26	12.529%	$238.8541	$238.85	$238.85	$238.90
7 purchase totals =	$945.01		$1,032.4312	$1,032.43	$1,032.40	$1,032.50