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	$144.28	5.627%	$152.3986	$152.40	$152.40	$152.40
Purchase #2	$216.41	10.289%	$238.6764	$238.68	$238.70	$238.70
Purchase #3	$135.96	12.382%	$152.7946	$152.79	$152.80	$152.80
Purchase #4	$118.85	10.641%	$131.4968	$131.50	$131.50	$131.50
Purchase #5	$12.97	8.369%	$14.0555	$14.06	$14.05	$14.10
Purchase #6	$99.45	3.219%	$102.6513	$102.65	$102.65	$102.70
Purchase #7	$241.90	9.565%	$265.0377	$265.04	$265.05	$265.00
7 purchase totals =	$969.82		$1,057.1109	$1,057.12	$1,057.15	$1,057.20