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	$148.94	10.382%	$164.403	$164.40	$164.40	$164.40
Purchase #2	$166.88	3.207%	$172.2318	$172.23	$172.25	$172.20
Purchase #3	$119.96	9.794%	$131.7089	$131.71	$131.70	$131.70
Purchase #4	$143.28	9.273%	$156.5664	$156.57	$156.55	$156.60
Purchase #5	$117.54	4.682%	$123.0432	$123.04	$123.05	$123.00
Purchase #6	$133.73	3.314%	$138.1618	$138.16	$138.15	$138.20
Purchase #7	$168.51	13.254%	$190.8443	$190.84	$190.85	$190.80
7 purchase totals =	$998.84		$1,076.9594	$1,076.95	$1,076.95	$1,076.90