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	$62.97	4.458%	$65.7772	$65.78	$65.80	$65.80
Purchase #2	$191.51	4.202%	$199.5573	$199.56	$199.55	$199.60
Purchase #3	$55.90	5.559%	$59.0075	$59.01	$59.00	$59.00
Purchase #4	$151.89	4.838%	$159.2384	$159.24	$159.25	$159.20
Purchase #5	$19.44	12.401%	$21.8508	$21.85	$21.85	$21.90
Purchase #6	$182.30	12.154%	$204.4567	$204.46	$204.45	$204.50
Purchase #7	$184.47	12.789%	$208.0619	$208.06	$208.05	$208.10
7 purchase totals =	$848.48		$917.9498	$917.96	$917.95	$918.10