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	$121.68	10.604%	$134.5829	$134.58	$134.60	$134.60
Purchase #2	$158.29	3.760%	$164.2417	$164.24	$164.25	$164.20
Purchase #3	$234.93	9.211%	$256.5694	$256.57	$256.55	$256.60
Purchase #4	$34.45	9.625%	$37.7658	$37.77	$37.75	$37.80
Purchase #5	$100.69	3.859%	$104.5756	$104.58	$104.60	$104.60
Purchase #6	$190.49	10.589%	$210.661	$210.66	$210.65	$210.70
Purchase #7	$182.78	11.705%	$204.1744	$204.17	$204.15	$204.20
7 purchase totals =	$1,023.31		$1,112.5708	$1,112.57	$1,112.55	$1,112.70