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	$148.81	3.222%	$153.6047	$153.60	$153.60	$153.60
Purchase #2	$50.96	8.377%	$55.2289	$55.23	$55.25	$55.20
Purchase #3	$147.32	12.770%	$166.1328	$166.13	$166.15	$166.10
Purchase #4	$199.87	4.405%	$208.6743	$208.67	$208.65	$208.70
Purchase #5	$113.61	3.680%	$117.7908	$117.79	$117.80	$117.80
Purchase #6	$51.45	4.707%	$53.8718	$53.87	$53.85	$53.90
Purchase #7	$169.55	9.457%	$185.5843	$185.58	$185.60	$185.60
7 purchase totals =	$881.57		$940.8876	$940.87	$940.90	$940.90