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	$106.37	10.601%	$117.6463	$117.65	$117.65	$117.60
Purchase #2	$150.97	12.346%	$169.6088	$169.61	$169.60	$169.60
Purchase #3	$187.81	6.607%	$200.2186	$200.22	$200.20	$200.20
Purchase #4	$96.42	9.812%	$105.8807	$105.88	$105.90	$105.90
Purchase #5	$65.25	8.861%	$71.0318	$71.03	$71.05	$71.00
Purchase #6	$60.48	10.379%	$66.7572	$66.76	$66.75	$66.80
Purchase #7	$121.29	13.128%	$137.213	$137.21	$137.20	$137.20
7 purchase totals =	$788.59		$868.3564	$868.36	$868.35	$868.30