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	$65.62	9.812%	$72.0586	$72.06	$72.05	$72.10
Purchase #2	$152.86	10.514%	$168.9317	$168.93	$168.95	$168.90
Purchase #3	$117.94	9.174%	$128.7598	$128.76	$128.75	$128.80
Purchase #4	$158.53	6.309%	$168.5317	$168.53	$168.55	$168.50
Purchase #5	$36.60	7.669%	$39.4069	$39.41	$39.40	$39.40
Purchase #6	$89.95	13.367%	$101.9736	$101.97	$101.95	$102.00
Purchase #7	$97.27	6.537%	$103.6285	$103.63	$103.65	$103.60
7 purchase totals =	$718.77		$783.2908	$783.29	$783.30	$783.30