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	$126.30	6.528%	$134.5449	$134.54	$134.55	$134.50
Purchase #2	$227.40	10.661%	$251.6431	$251.64	$251.65	$251.60
Purchase #3	$195.89	7.525%	$210.6307	$210.63	$210.65	$210.60
Purchase #4	$81.69	9.527%	$89.4726	$89.47	$89.45	$89.50
Purchase #5	$132.95	6.774%	$141.956	$141.96	$141.95	$142.00
Purchase #6	$12.92	10.546%	$14.2825	$14.28	$14.30	$14.30
Purchase #7	$130.75	8.493%	$141.8546	$141.85	$141.85	$141.90
7 purchase totals =	$907.90		$984.3844	$984.37	$984.40	$984.40