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	$81.71	4.710%	$85.5585	$85.56	$85.55	$85.60
Purchase #2	$223.42	9.463%	$244.5622	$244.56	$244.55	$244.60
Purchase #3	$232.32	12.126%	$260.4911	$260.49	$260.50	$260.50
Purchase #4	$50.67	10.195%	$55.8358	$55.84	$55.85	$55.80
Purchase #5	$49.46	8.240%	$53.5355	$53.54	$53.55	$53.50
Purchase #6	$43.71	12.240%	$49.0601	$49.06	$49.05	$49.10
Purchase #7	$231.57	12.523%	$260.5695	$260.57	$260.55	$260.60
7 purchase totals =	$912.86		$1,009.6127	$1,009.62	$1,009.60	$1,009.70