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	$139.89	6.224%	$148.5968	$148.60	$148.60	$148.60
Purchase #2	$36.29	9.106%	$39.5946	$39.59	$39.60	$39.60
Purchase #3	$6.78	9.633%	$7.4331	$7.43	$7.45	$7.40
Purchase #4	$219.39	4.131%	$228.453	$228.45	$228.45	$228.50
Purchase #5	$221.93	10.292%	$244.771	$244.77	$244.75	$244.80
Purchase #6	$98.34	4.249%	$102.5185	$102.52	$102.50	$102.50
Purchase #7	$96.45	9.715%	$105.8201	$105.82	$105.80	$105.80
7 purchase totals =	$819.07		$877.1871	$877.18	$877.15	$877.20