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	$205.89	3.710%	$213.5285	$213.53	$213.55	$213.50
Purchase #2	$65.82	10.618%	$72.8088	$72.81	$72.80	$72.80
Purchase #3	$157.68	12.767%	$177.811	$177.81	$177.80	$177.80
Purchase #4	$149.74	10.601%	$165.6139	$165.61	$165.60	$165.60
Purchase #5	$45.56	4.192%	$47.4699	$47.47	$47.45	$47.50
Purchase #6	$219.31	11.613%	$244.7785	$244.78	$244.80	$244.80
Purchase #7	$37.81	4.677%	$39.5784	$39.58	$39.60	$39.60
7 purchase totals =	$881.81		$961.5890	$961.59	$961.60	$961.60