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	$64.62	8.662%	$70.2174	$70.22	$70.20	$70.20
Purchase #2	$199.72	11.346%	$222.3802	$222.38	$222.40	$222.40
Purchase #3	$32.38	6.851%	$34.5984	$34.60	$34.60	$34.60
Purchase #4	$82.45	10.677%	$91.2532	$91.25	$91.25	$91.30
Purchase #5	$38.45	11.273%	$42.7845	$42.78	$42.80	$42.80
Purchase #6	$117.40	13.209%	$132.9074	$132.91	$132.90	$132.90
Purchase #7	$238.48	13.536%	$270.7607	$270.76	$270.75	$270.80
7 purchase totals =	$773.50		$864.9018	$864.90	$864.90	$865.00