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	$198.32	13.682%	$225.4541	$225.45	$225.45	$225.50
Purchase #2	$216.40	10.399%	$238.9034	$238.90	$238.90	$238.90
Purchase #3	$95.45	10.210%	$105.1954	$105.20	$105.20	$105.20
Purchase #4	$137.36	12.423%	$154.4242	$154.42	$154.40	$154.40
Purchase #5	$92.32	12.244%	$103.6237	$103.62	$103.60	$103.60
Purchase #6	$105.29	13.260%	$119.2515	$119.25	$119.25	$119.30
Purchase #7	$159.88	6.659%	$170.5264	$170.53	$170.55	$170.50
7 purchase totals =	$1,005.02		$1,117.3787	$1,117.37	$1,117.35	$1,117.40