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	$157.32	7.430%	$169.0089	$169.01	$169.00	$169.00
Purchase #2	$104.39	9.794%	$114.614	$114.61	$114.60	$114.60
Purchase #3	$36.39	3.429%	$37.6378	$37.64	$37.65	$37.60
Purchase #4	$42.61	11.526%	$47.5212	$47.52	$47.50	$47.50
Purchase #5	$155.45	6.854%	$166.1045	$166.10	$166.10	$166.10
Purchase #6	$148.79	4.555%	$155.5674	$155.57	$155.55	$155.60
Purchase #7	$155.46	10.819%	$172.2792	$172.28	$172.30	$172.30
7 purchase totals =	$800.41		$862.7330	$862.73	$862.70	$862.70