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	$62.58	4.680%	$65.5087	$65.51	$65.50	$65.50
Purchase #2	$25.76	13.787%	$29.3115	$29.31	$29.30	$29.30
Purchase #3	$190.32	9.502%	$208.4042	$208.40	$208.40	$208.40
Purchase #4	$182.54	9.805%	$200.438	$200.44	$200.45	$200.40
Purchase #5	$142.42	8.789%	$154.9373	$154.94	$154.95	$154.90
Purchase #6	$64.90	13.820%	$73.8692	$73.87	$73.85	$73.90
Purchase #7	$200.95	12.155%	$225.3755	$225.38	$225.40	$225.40
7 purchase totals =	$869.47		$957.8444	$957.85	$957.85	$957.80