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	$114.74	7.312%	$123.1298	$123.13	$123.15	$123.10
Purchase #2	$149.54	11.426%	$166.6264	$166.63	$166.65	$166.60
Purchase #3	$145.70	12.871%	$164.453	$164.45	$164.45	$164.50
Purchase #4	$114.44	3.544%	$118.4958	$118.50	$118.50	$118.50
Purchase #5	$243.54	10.291%	$268.6027	$268.60	$268.60	$268.60
Purchase #6	$236.33	9.110%	$257.8597	$257.86	$257.85	$257.90
Purchase #7	$43.70	10.178%	$48.1478	$48.15	$48.15	$48.10
7 purchase totals =	$1,047.99		$1,147.3152	$1,147.32	$1,147.35	$1,147.30