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	$190.56	5.190%	$200.4501	$200.45	$200.45	$200.50
Purchase #2	$208.60	8.208%	$225.7219	$225.72	$225.70	$225.70
Purchase #3	$27.88	11.541%	$31.0976	$31.10	$31.10	$31.10
Purchase #4	$83.52	7.813%	$90.0454	$90.05	$90.05	$90.00
Purchase #5	$100.99	13.248%	$114.3692	$114.37	$114.35	$114.40
Purchase #6	$36.35	3.251%	$37.5317	$37.53	$37.55	$37.50
Purchase #7	$158.25	12.164%	$177.4995	$177.50	$177.50	$177.50
7 purchase totals =	$806.15		$876.7154	$876.72	$876.70	$876.70