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	$164.50	4.556%	$171.9946	$171.99	$172.00	$172.00
Purchase #2	$199.92	10.851%	$221.6133	$221.61	$221.60	$221.60
Purchase #3	$148.90	11.856%	$166.5536	$166.55	$166.55	$166.60
Purchase #4	$211.69	4.786%	$221.8215	$221.82	$221.80	$221.80
Purchase #5	$205.36	7.364%	$220.4827	$220.48	$220.50	$220.50
Purchase #6	$66.86	5.400%	$70.4704	$70.47	$70.45	$70.50
Purchase #7	$100.25	3.626%	$103.8851	$103.89	$103.90	$103.90
7 purchase totals =	$1,097.48		$1,176.8212	$1,176.81	$1,176.80	$1,176.90